CN108798864B - Cooling device for internal combustion engine - Google Patents

Abstract

A cooling device for an internal combustion engine, comprising: a pump section that pressure-feeds cooling water; a circulation water channel formed to return the cooling water from the pump section to the pump section again through the engine water channel; a thermostat that switches between a state in which cooling water flows through a heat exchange water passage in which a radiator is disposed and a state in which cooling water does not flow through the heat exchange water passage; and a control unit that controls the pump section. The control unit controls the three-way valve to connect the 1 st pump and the 2 nd pump in parallel when the thermostat is switched to a state in which the cooling water flows through the heat-exchange water passage, and controls the three-way valve to connect the 1 st pump and the 2 nd pump in series when the thermostat is switched to a state in which the cooling water does not flow through the heat-exchange water passage.

Description

Cooling device for internal combustion engine

Technical Field

The present invention relates to a cooling device for an internal combustion engine.

Background

There is known a cooling device for an internal combustion engine, which circulates cooling water discharged from a pump through the internal combustion engine and a heat exchanger to cool the internal combustion engine. In particular, since the flow rate of the cooling water required for cooling increases with an increase in size of the internal combustion engine, it has been studied to increase the output of the pump. However, it is necessary to increase the size of the pump in order to increase the output of the pump, but it is difficult to secure a large concentrated space for mounting the bulky pump around the engine main body. Therefore, the following techniques are known: in order to increase the flow rate without increasing the volume of each pump, two pumps are connected in parallel (japanese patent laid-open No. 2016-.

Disclosure of Invention

It is known that: the cooling device for an internal combustion engine includes a heat exchanger provided in parallel to cooling water via a pump and a circulation water path of the internal combustion engine. In the cooling device as described above, the cooling water flows relatively easily when the cooling water flows through the circulation water passage and the heat exchanger, and the cooling water flows relatively hardly when the cooling water flows only through the circulation water passage. For example, when the cooling water is relatively easy to flow, a sufficient flow rate can be ensured even if the water pressure of the cooling water discharged from the pump is low. Therefore, in this case, the pumps are connected in parallel, whereby the capacity of the pumps can be increased and the flow rate can be increased.

On the other hand, when the coolant is relatively difficult to flow, if the water pressure of the coolant discharged from the pump is low, a sufficient flow rate cannot be secured. When the pumps are connected in parallel as described above, the water pressure that can be output by the entire pump is equal to the water pressure that can be output by one of the pumps. As a result, the water pressure of the cooling water discharged from the entire pump cannot be increased. Therefore, when the cooling water is difficult to flow to the cooling device, a sufficient flow rate cannot be secured even if the pumps are connected in parallel.

Therefore, it is difficult to supply a sufficient amount of cooling water from the pumps without increasing the volume of each pump.

The invention provides a cooling device capable of supplying a sufficient amount of cooling water from a pump without increasing the volume of each pump.

The cooling device for an internal combustion engine according to an aspect of the present invention includes: a pump section that pressure-feeds cooling water of the internal combustion engine; and a circulation water channel including an engine water channel of an internal combustion engine, the circulation water channel being configured to connect a pump portion and the engine water channel such that the cooling water pumped from the pump portion passes through the engine water channel and returns to the pump portion again. The cooling device for an internal combustion engine includes: a heat exchanger configured to exchange heat with cooling water; and a heat-exchange water path in which the heat exchanger is disposed and which is provided in parallel with at least a part of the circulation water path. The cooling device for an internal combustion engine includes: a water passage switching device that switches between a state in which cooling water flows through the heat exchange water passage and a state in which cooling water does not flow through the heat exchange water passage; and a control device that controls the pump unit.

The pump section includes a 1 st pump, a 2 nd pump, and a pump switching device that switches between a state in which the 1 st pump and the 2 nd pump are connected in parallel and a state in which the 1 st pump and the 2 nd pump are connected in series. The control device is configured to control the pump switching device to connect the 1 st pump and the 2 nd pump in parallel when the water path switching device is switched to a state in which the cooling water flows in the heat exchange water path and the cooling water flows in the circulation water path and the heat exchange water path. On the other hand, the control device is configured to control the pump switching device so as to connect the 1 st pump and the 2 nd pump in series when the water channel switching device is switched to a state in which the cooling water does not flow through the heat exchange water channel and the cooling water flows only through the circulation water channel.

In the aspect of the present invention, the water path switching device may be a thermostat that is provided in the heat exchange water path and switches between an open state and a closed state according to a temperature of the cooling water. The thermostat may be configured such that the cooling water flows through the heat-exchange water passage when the thermostat is in an open state, and the thermostat may be configured such that the flow of the cooling water through the heat-exchange water passage is stopped when the thermostat is in a closed state.

In the aspect of the present invention, when the water channel switching device is switched to the state in which the cooling water flows in the heat exchange water channel, the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in parallel may be larger than the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in series. When the water channel switching device is switched to a state in which the cooling water is not flowing through the heat exchange water channel, the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in parallel may be smaller than the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in series.

In the aspect of the present invention, the circulation water path and the heat-exchange water path may be configured such that a flow path resistance of a path of the cooling water becomes equal to or less than a reference flow path resistance when the water path switching device is switched to a state in which the cooling water flows in the heat-exchange water path, and the flow path resistance of the path of the cooling water is greater than the reference flow path resistance when the water path switching device is switched to a state in which the cooling water does not flow in the heat-exchange water path. When a curve showing a relationship between a flow rate and a water pressure when a flow path resistance of the cooling water path is an arbitrary value is defined as a resistance curve, the reference flow path resistance may be a flow path resistance when the resistance curve passes through an intersection of a parallel characteristic curve and a series characteristic curve. The parallel characteristic curve may be a curve showing a relationship between a maximum flow rate and a maximum water pressure that can be output by the pump unit in a state where the 1 st pump and the 2 nd pump are connected in parallel. The series characteristic curve may be a curve showing a relationship between a maximum flow rate and a maximum water pressure that can be output by the pump unit in a state where the 1 st pump and the 2 nd pump are connected in series.

In the aspect of the present invention, the control device may be configured to control the pump switching device to connect the 1 st pump and the 2 nd pump in parallel and to drive only one of the 1 st pump and the 2 nd pump regardless of a state of the water channel switching device when a requested flow rate to the pump portion is less than a preset flow rate.

In the technical solution of the present invention, the heat exchanger may include a 1 st heat exchanger and a 2 nd heat exchanger. The heat-exchange water path may include a 1 st heat-exchange water path and a 2 nd heat-exchange water path, the 1 st heat-exchange water path may be provided with the 1 st heat exchanger and may be provided in parallel with at least a part of the circulation water path, and the 2 nd heat-exchange water path may be provided with the 2 nd heat exchanger and may be provided in parallel with at least a part of the circulation water path. The water path switching device may include a 1 st water path switching device and a 2 nd water path switching device, the 1 st water path switching device may switch between a state in which the cooling water flows in the 1 st heat-exchange water path and a state in which the cooling water does not flow in the 1 st heat-exchange water path, and the 2 nd water path switching device may switch between a state in which the cooling water flows in the 2 nd heat-exchange water path and a state in which the cooling water does not flow in the 2 nd heat-exchange water path. When the water path switching device is switched to the state in which the cooling water flows through the heat-exchange water path, the 1 st water path switching device may be switched to the state in which the cooling water flows through the 1 st heat-exchange water path and the 2 nd water path switching device may be switched to the state in which the cooling water flows through the 2 nd heat-exchange water path. When the water path switching device is switched to the state in which the cooling water does not flow through the heat-exchange water path, the 1 st water path switching device may be switched to the state in which the cooling water does not flow through the 1 st heat-exchange water path and the 2 nd water path switching device may be switched to the state in which the cooling water does not flow through the 2 nd heat-exchange water path.

In the aspect of the present invention, the control device may be configured to store, as the 1 st area, an area in which the flow rate and the water pressure can be output only by connecting the 1 st pump and the 2 nd pump in parallel when the 1 st water path switching device and the 2 nd water path switching device are switched to a state in which the cooling water flows in either the 1 st heat-exchange water path or the 2 nd heat-exchange water path. The control device may be configured to store, as the 2 nd area, an area in which only the flow rate and the water pressure that can be output by connecting the 1 st pump and the 2 nd pump in series are stored when the 1 st water path switching device and the 2 nd water path switching device are switched to a state in which the cooling water flows in either one of the 1 st heat-exchange water path and the 2 nd heat-exchange water path. The control device may be configured to calculate a requested flow rate to the pump unit and a requested water pressure to the pump unit, which is determined by the requested flow rate, the state of the 1 st water channel switching device, and the state of the 2 nd water channel switching device. The control device may be configured to control the pump switching device to connect the 1 st pump and the 2 nd pump in parallel when the requested flow rate and the requested water pressure are included in the 1 st region. The control device may be configured to control the pump switching device to connect the 1 st pump and the 2 nd pump in series when the requested flow rate and the requested water pressure are included in the 2 nd range.

In the aspect of the present invention, the pump unit may include a 1 st pump that pumps cooling water, a 2 nd pump that pumps cooling water, an inlet water passage into which cooling water flows, an outlet water passage from which cooling water flows, a 1 st water passage in which the 1 st pump is disposed, a 2 nd water passage in which the 2 nd pump is disposed, an inter-pump water passage, and a check valve. The 1 st water path and the 2 nd water path may communicate with the inlet water path at a branch point, be arranged in parallel with each other, and communicate with the outlet water path at a confluence point. The inter-pump water passage may communicate a water passage on the cooling water discharge side of the 1 st pump in the 1 st water passage with a water passage on the cooling water suction side of the 2 nd pump in the 2 nd water passage. The check valve may be disposed in the 2 nd water path between a connection portion of the 2 nd water path and the inter-pump water path and the branch point. The pump switching device may be a three-way valve provided at a connection portion between the 1 st water path and the inter-pump water path. The three-way valve may be configured to selectively switch between a 1 st switching position and a 2 nd switching position, the 1 st switching position being a switching position at which the coolant flowing through the 1 st water path flows directly into the 1 st water path without flowing into the inter-pump water path, and the 2 nd switching position being a switching position at which the coolant flowing through the 1 st water path flows into the inter-pump water path without flowing directly into the 1 st water path. The controller may be configured to switch the three-way valve to the 1 st switching position when the 1 st pump and the 2 nd pump are connected in parallel, and to switch the three-way valve to the 2 nd switching position when the 1 st pump and the 2 nd pump are connected in series.

In the aspect of the present invention, the pump unit may include a 1 st pump that pumps cooling water, a 2 nd pump that pumps cooling water, an inlet water passage into which cooling water flows, an outlet water passage from which cooling water flows, a 1 st water passage in which the 1 st pump is disposed, a 2 nd water passage in which the 2 nd pump is disposed, an inter-pump water passage, a 1 st check valve, a 2 nd check valve, and a pump switching device. The 1 st water path and the 2 nd water path may communicate with the inlet water path at a branch point, be provided in parallel with each other, and communicate with the outlet water path at a confluence point of the 1 st water path and the 2 nd water path. The inter-pump water passage may communicate a water passage on the cooling water discharge side of the 1 st pump in the 1 st water passage with a water passage on the cooling water suction side of the 2 nd pump in the 2 nd water passage. The 1 st check valve may be disposed in the 2 nd water path between a connection portion of the 2 nd water path and the inter-pump water path and the branch point. The 2 nd check valve may be disposed in the 1 st water path between a connection portion of the 1 st water path and the inter-pump water path and the confluence point. The pump switching device may be disposed in the inter-pump water passage. The 1 st pump may be disposed in the 1 st water path between a connection portion between the 1 st water path and the inter-pump water path and the branch point. The 2 nd pump may be disposed in the 2 nd water path between a connection portion between the 2 nd water path and the inter-pump water path and the confluence point. The pump switching device may be an on-off valve provided in the inter-pump water passage. The on-off valve may be configured to selectively switch between a 1 st switching position for closing the inter-pump water passage and a 2 nd switching position for opening the inter-pump water passage. The control device may be configured to set the on-off valve to the 1 st switching position when the 1 st pump and the 2 nd pump are connected in parallel, and set the on-off valve to the 2 nd switching position when the 1 st pump and the 2 nd pump are connected in series.

According to the aspect of the present invention, a sufficient amount of cooling water can be supplied from the pump without increasing the volume of each pump.

Drawings

The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, wherein like reference numerals represent like parts, and in which:

fig. 1 is a schematic diagram showing a cooling apparatus for an internal combustion engine according to embodiment 1 of the present invention.

Fig. 2 is a graph of a resistance curve showing a relationship between the water pressure and the flow rate of the cooling water discharged from the pump.

Fig. 3 is a graph showing the characteristic curve of a single pump versus the resistance curve.

Fig. 4A is a schematic diagram showing a case where pumps are connected in parallel.

Fig. 4B is a graph showing a relationship between a characteristic curve and a resistance curve in the case where pumps are connected in parallel.

Fig. 5A is a schematic diagram showing a case where pumps are connected in series.

Fig. 5B is a graph showing a relationship between a characteristic curve and a resistance curve in the case where pumps are connected in series.

Fig. 6 is a schematic diagram showing a state of the cooling apparatus for an internal combustion engine in the case where the cooling water flows through the radiator and the bypass water passage in embodiment 1 of the present invention.

Fig. 7 is a schematic diagram showing a state of the cooling apparatus for an internal combustion engine in the case where the cooling water flows only through the bypass water passage in embodiment 1 of the present invention.

Fig. 8 is a graph showing a change in the pump connection method according to a change in the flow path resistance.

Fig. 9 is a schematic diagram showing a cooling apparatus for an internal combustion engine according to embodiment 2 of the present invention.

Fig. 10 is a schematic diagram showing a cooling apparatus for an internal combustion engine according to embodiment 3 of the present invention.

Fig. 11 is a schematic diagram showing a cooling apparatus for an internal combustion engine according to embodiment 4 of the present invention.

Fig. 12 is a schematic diagram showing a cooling apparatus for an internal combustion engine according to embodiment 5 of the present invention.

Fig. 13 is a flowchart showing a routine of the 1 st control example of the present invention.

Fig. 14 is a graph showing a change in the pump connection method according to the control example 2 of the present invention.

Fig. 15 is a flowchart showing a routine of a control example 2 of the present invention.

Fig. 16 is a flowchart showing a routine of a control example 3 of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same components are denoted by the same reference numerals.

Fig. 1 is a schematic diagram showing a cooling apparatus for an internal combustion engine according to embodiment 1 of the present invention. The cooling device 100 for an internal combustion engine according to embodiment 1 includes an engine main body 1, a heat exchange unit 2, and a pump unit 3. The engine body 1, the heat exchange unit 2, and the pump unit 3 are annularly connected by cooling water channels, and are arranged such that cooling water circulates in the order of the engine body 1, the heat exchange unit 2, and the pump unit 3.

The engine body 1 combusts fuel in a combustion chamber provided inside the engine body 1 to generate driving force. The engine body 1 is heated to a high temperature by the combustion of the fuel, and therefore, cooling is required. In the present embodiment, cooling water is used for cooling the engine body 1. An engine water passage through which cooling water flows is provided inside the engine main body 1, and the engine main body 1 is cooled by radiating heat to the outside of the engine main body 1 via the cooling water flowing through the engine water passage. For example, the engine water path includes a water jacket formed around a combustion chamber of the cylinder block and/or a cooling water path formed in the cylinder head.

The heat exchanger 2 is a device for exchanging heat between the cooling water and the outside of the internal combustion engine. In the present embodiment, the heat exchange portion 2 is disposed downstream of the engine main body 1, and the cooling water heated by the engine main body 1 is cooled by the heat exchange portion 2.

In the present embodiment, as shown in fig. 1, the heat exchanger 2 includes a radiator 21, a thermostat 22, a heat exchange water passage 23, and a bypass water passage 24. The radiator 21 and the thermostat 22 are provided in the heat-exchange water passage 23, and a bypass water passage 24 is provided so as to bypass the radiator 21 and the thermostat 22.

The radiator 21 allows the cooling water to flow through the radiator 21, thereby releasing the heat of the cooling water to the outside. Since the heat of the cooling water is released to the outside through the wall surface of the water channel provided in the radiator 21, the larger the contact area between the cooling water and the wall surface of the water channel, that is, the larger the surface area of the wall surface of the water channel, the more efficiently the cooling water can be cooled. In the present embodiment, in order to increase the surface area of the water passage of the radiator 21, the diameter of each water passage provided in the radiator 21 is designed to be smaller than the diameter of the water passage of the bypass water passage 24.

The thermostat 22 is disposed in the heat-exchange water passage 23 on the downstream side of the radiator 21, and is capable of selectively switching between an open state in which the flow of the cooling water through the heat-exchange water passage 23 is permitted and a closed state in which the flow of the cooling water is blocked. In the present embodiment, since the radiator 21 and the thermostat 22 are provided in series in the heat-exchange water passage 23, the state of the thermostat 22 is switched, and the state of the cooling water flowing through the radiator 21 is switched.

In the present embodiment, the thermostat 22 is provided with a member that contacts the valve body of the thermostat 22, expands when the temperature of the cooling water increases, and contracts when the temperature of the cooling water decreases. The thermostat 22 is opened when the component is expanded, and the thermostat 22 is closed when the component is contracted. Therefore, the thermostat 22 automatically turns to the open state when the temperature of the cooling water is equal to or higher than a predetermined temperature, and the thermostat 22 automatically turns to the closed state when the temperature of the cooling water is lower than the predetermined temperature.

As a result, in the present embodiment, when the temperature of the cooling water is low, the thermostat 22 is in the closed state. As a result, the cooling water flows only through the bypass water path 24 and not through the heat-exchange water path 23. Therefore, the flow of the cooling water to the radiator 21 is blocked, and the cooling of the cooling water can be suppressed. On the other hand, when the temperature of the cooling water is high, the thermostat 22 is opened. As a result, the cooling water flows through both the heat-exchange water passage 23 and the bypass water passage 24. Therefore, the cooling water flows through the radiator 21. As a result, the cooling water is cooled.

Alternatively, the open state of the thermostat 22 or the closed state of the thermostat 22 may be controlled by an actuator.

In the present embodiment, a water channel in which the cooling water discharged from the pump portion 3 is returned to the pump portion 3 again via the engine water channel of the engine main body 1 and the bypass water channel 24 is referred to as a "circulation water channel". Therefore, in the embodiment shown in fig. 1, the circulating water path is constituted by a cooling water path from the pump portion 3 to the engine main body 1, an engine water path, a cooling water path from the engine main body 1 to the bypass water path 24, and a cooling water path from the bypass water path 24 to the pump portion 3. A heat exchange water passage 23 in which the radiator 21 is disposed is provided in parallel with a part of the circulation water passage. The cooling water always flows through the circulation water path, and whether the cooling water flows through the heat exchange water path 23 or not is controlled by the thermostat 22. In the present embodiment, the engine water passage and the bypass water passage 24 of the engine body 1 are part of the circulation water passage.

The pump section 3 increases the water pressure of the cooling water to circulate the cooling water through the engine body 1 and the heat exchange section 2. In the present embodiment, as shown in fig. 1, the pump section 3 includes a 1 st pump 31, a 2 nd pump 32, a three-way valve 38, and a check valve 39. The pump section 3 includes a 1 st water passage 33 and a 2 nd water passage 34 provided in parallel. The 1 st water path 33 and the 2 nd water path 34 communicate with the inlet water path 43 at the branch point 35 at the upstream ends thereof, and communicate with the outlet water path 44 at the junction point 36 at the downstream ends thereof. That is, in the pump section 3, the inlet water passage 43 branches at a branch point 35 into the 1 st water passage 33 and the 2 nd water passage 34, and the 1 st water passage 33 and the 2 nd water passage 34 join at a joining point 36 and lead to the outlet water passage 44. The 1 st water path 33 and the 2 nd water path 34 are connected at their respective intermediate portions by an inter-pump water path 37. Hereinafter, the connection portion between the 1 st water channel 33 and the inter-pump water channel 37 is referred to as "1 st connection portion 371", and the connection portion between the 2 nd water channel 34 and the inter-pump water channel 37 is referred to as "2 nd connection portion 372".

The 1 st pump 31 is disposed in the 1 st water passage 33 between the branch point 35 and the 1 st connection portion 371, and the 2 nd pump 32 is disposed in the 2 nd water passage 34 between the 2 nd connection portion 372 and the junction 36.

The 1 st pump 31 and the 2 nd pump 32 are pumps for pumping the cooling water. The 1 st pump 31 and the 2 nd pump 32 are respectively provided with an inlet port for supplying the cooling water and a discharge port for discharging the cooling water, and the cooling water supplied from the inlet port is pressurized by the 1 st pump 31 or the 2 nd pump 32 and discharged from the discharge port.

In the present embodiment, the 1 st pump 31 and the 2 nd pump 32 are electric pumps, and the 1 st pump 31 and the 2 nd pump 32 can control the water pressure of the discharged cooling water. In the present embodiment, the maximum water pressure of the cooling water that can be discharged by the 1 st pump 31 is lower than the maximum water pressure of the cooling water that can be discharged by the 2 nd pump 32. The 1 st pump 31 and the 2 nd pump 32 may have the same performance, that is, the maximum water pressure of the cooling water that can be discharged by the 1 st pump 31 and the 2 nd pump 32 is equal to each other.

The three-way valve 38 is provided at the 1 st connection 371. The three-way valve 38 is switchable between a 1 st switching position at which the cooling water flowing from the 1 st water passage 33 is directly circulated to the 1 st water passage 33, and a 2 nd switching position at which the cooling water flowing from the 1 st water passage 33 is flowed into the inter-pump water passage 37. The three-way valve 38 is controlled by receiving a signal from a control unit 200 described later.

The check valve 39 is a valve for allowing the cooling water to flow in one direction. In the present embodiment, the check valve 39 is disposed in the 2 nd water passage 34 between the branch point 35 and the 2 nd connection portion 372. The check valve 39 is configured to allow the coolant flowing from the branch point 35 toward the 2 nd connecting portion 372 to flow therethrough, but to prohibit the coolant from the 2 nd connecting portion 372 toward the branch point 35 from flowing therethrough.

In the present embodiment, the method of connecting the 1 st pump 31 and the 2 nd pump 32 can be switched between parallel connection and series connection by controlling the three-way valve 38 between the 1 st switching position and the 2 nd switching position.

Specifically, when the three-way valve 38 is switched to the 1 st switching position, the 1 st pump 31 and the 2 nd pump 32 are connected in parallel because the flow of the cooling water to the inter-pump water passage 37 is blocked. That is, the cooling water flowing into the pump unit 3 is branched into the 1 st water passage 33 and the 2 nd water passage 34 at the branch point 35, and is discharged by raising the water pressure by the 1 st pump 31 and the 2 nd pump 32, respectively. The cooling water discharged from the 1 st pump 31 and the 2 nd pump 32 flows toward the merging point 36 and is discharged to the outside of the pump section 3.

On the other hand, when the three-way valve 38 is switched to the 2 nd switching position, the 1 st pump 31 and the 2 nd pump 32 are connected in series so that the cooling water flows through the inter-pump water passage 37. That is, the cooling water flowing into the pump section 3 flows into the 1 st pump 31 through the branch point 35, and the water pressure is increased and discharged. The cooling water discharged from the 1 st pump 31 flows into the 2 nd water passage 34 through the three-way valve 38 and the inter-pump water passage 37. In this case, since the check valve 39 is provided between the branch point 35 and the 2 nd connection portion 372, the cooling water discharged from the 1 st pump 31 flows into the 2 nd pump 32 so as not to return to the branch point 35 through the 2 nd water passage 34. The cooling water flowing into the 2 nd pump 32 is discharged with the water pressure increased. The cooling water discharged from the 2 nd pump 32 flows toward the merging point 36 and is discharged from the pump section 3. In this case, the three-way valve 38 restricts the flow of the cooling water between the 1 st connection 371 and the junction 36, so that the cooling water does not flow.

The control unit 200 is constituted by a digital computer, and includes a ROM202, a RAM203, a CPU204, an input port 205, and an output port 206, which are connected to each other by a bidirectional bus 201.

The input port 205 is inputted with output signals of various sensors required for controlling the cooling device 100 of the internal combustion engine. In the present embodiment, an analog signal received from a water temperature sensor 5 for measuring the water temperature of the cooling water is converted into a digital signal by an AD converter 207 and input to the input port 205. In the present embodiment, the water temperature sensor 5 is provided in the water passage between the engine body 1 and the heat exchanger 2.

In the present embodiment, the output port 206 outputs the digital signal calculated by the CPU204 to the 1 st pump 31, the 2 nd pump 32, and the three-way valve 38.

Here, before describing an embodiment of the present invention, general properties related to discharge of liquid using a pump will be described. Fig. 2 is a graph showing a relationship between a flow rate Q (horizontal axis) per unit time of a liquid discharged from a pump disposed in a certain water channel and a water pressure P (vertical axis) of the pump required to output the flow rate Q.

As shown by a solid line Lr in fig. 2, when the water pressure of the liquid discharged from the pump is P, the flow rate of the liquid discharged from the pump becomes Q. The relationship between the water pressure P and the flow rate Q changes according to the difficulty of flowing the liquid in the water channel in which the pump is disposed. Hereinafter, a curve showing a relationship between the water pressure P and the flow rate Q is referred to as a "resistance curve".

In general, the resistance curve is a 2-degree function of the flow rate Q, i.e., P ═ R × Q²Such a formal representation. Here, the coefficient R is a value indicating how difficult the liquid in the water path in which the pump is disposed flows, and is referred to as "flow path resistance". The flow path resistance R is determined according to the shape of a water path for the pump to flow the liquid. For example, when the length of the water path becomes longer, the liquid becomes more difficult to flow, so the flow path resistance R becomes larger. The resistance curve when the flow path resistance R becomes large is shown by the broken line Lrh in fig. 2. On the other hand, when the diameter of the water path is increased, the liquid flows easily, and thus the flow path resistance R is decreased. The resistance curve when the flow path resistance R becomes small is shown by the dashed-dotted line Lrl in fig. 2.

In the case where the pump is driven by a motor, the flow rate Q and the water pressure P that the pump can discharge can be determined according to the maximum output of the motor. Fig. 3 is a graph showing the ranges of the flow rate Q and the water pressure P that the pump can discharge.

The ranges of the flow rate Q and the water pressure P that the single pump WPA can discharge are indicated by a region a surrounded by a solid line Lpa of fig. 3. A solid line Lpa surrounding the area a of fig. 3 shows a relationship between the flow rate Q and the water pressure P when the pump WPA is driven at the maximum output, and the solid line Lpa is referred to as a "pump characteristic curve".

By using the pump characteristic curve, the flow rate Q that can be discharged by the pump can be calculated when the configuration of the water passage is determined and the flow path resistance R of the water passage is determined. For example, when the flow path resistance R is R1 and the resistance curve is a curve indicated by a dashed-dotted line Lrl in fig. 3, a water pressure of P1 is required to discharge the liquid from the pump WPA at the flow rate Q1, and a water pressure of P2 is required to discharge the liquid at the flow rate Q2 larger than the flow rate Q1. In the above case, since the flow rate Q1 and the water pressure P1 are included in the region a, it can be determined that the discharge by the pump WPA is possible, and since the flow rate Q2 and the water pressure P2 are not included in the region a, it can be determined that the discharge by the pump WPA is impossible.

Here, a case is considered where the pump WPB is used to discharge the liquid having the flow rate Q2, which can generate a larger output than the pump WPA. As shown in fig. 3, since the output of the pump WPB is larger than the output of the pump WPA, the pump characteristic curve of the pump WPB is located outside the pump characteristic curve of the pump WPA and indicated by a solid line Lpb. Therefore, the pump WPB can discharge the fluid at the flow rate Q and the water pressure P included in the region a or the region B inside the pump characteristic curve.

Here, again, consider a case where the liquid is discharged at the flow rate Q2 using the pump WPB with respect to a water path having the same flow path resistance R as in the above example. In this case, since the flow rate Q2 and the water pressure P2 are included in the region B, the pump WPB can discharge the liquid in the amount of the flow rate Q2. As described above, the flow rate Q of the liquid that can be discharged from the pump can be increased by increasing the output of the pump by setting the pump WPA as the pump WPB.

When discharging a flow rate Q larger than the range B, a pump having a larger output may be used. However, in order to increase the output of the pump, the volume of the pump must be increased. In the case described above, there is a problem that a large space for mounting the pump must be secured in the vehicle.

It is easier to secure a plurality of small spaces than to secure one large space. Therefore, a case where a plurality of pumps are used to discharge the liquid at the flow rate Q3 outside the range of the region B without increasing the volume of each pump was examined.

By connecting the pumps in parallel, the flow rate of the liquid discharged from the pumps can be increased. First, a case where the pumps are connected in parallel as described above will be described below.

Fig. 4A shows a positional relationship in a case where the pump WPA and the pump WPB are arranged in parallel. As shown in fig. 4A, the liquid supplied to the point P _ in is branched into the pump WPA and the pump WPB. Thereafter, the liquid whose pressure has been increased by the pump WPA and the liquid whose pressure has been increased by the pump WPB merge, and are discharged from the point P _ out.

As described above, since the pressure of the liquid supplied to the point P _ in is increased and the liquid is discharged from the point P _ out, the pump and the water path from the point P _ in to the point P _ out can be regarded as one pump. Therefore, the pump formed by arranging the pump WPA and the pump WPB in parallel is referred to as a pump WPC.

The characteristics of the pump WPC as described above are as follows. First, in fig. 4A, since the pressure of the liquid is increased by one of the pump WPA and the pump WPB, the water pressure PC that can be output by the pump WPC is the same as the water pressure that can be output by the pump WPA or the pump WPB alone. On the other hand, since the liquid pressurized by the pump WPA and the liquid pressurized by the pump WPB merge, the flow rate QC that can be discharged by the pump WPC is the sum of the flow rate QA that can be discharged by the pump WPA and the flow rate QB that can be discharged by the pump WPB. That is, the relationship QC ═ QA + QB holds.

The solid line Lpc of fig. 4B is a graph showing a pump characteristic curve of the pump WPC. As described above, since the relationship QC ═ QA + QB is established, the pump characteristic curve of the pump WPC is a curve obtained by adding the pump characteristic curve of the pump WPA (solid line Lpa) and the pump characteristic curve of the pump WPB (solid line Lpb) in the direction of the flow rate Q. The range in which the output of the pump WPC can be used is a range surrounded by the pump characteristic curve of the pump WPC, and therefore is the region a, the region B, and the region C. That is, by arranging the pump WPA and the pump WPB in parallel, the region in which the output can be performed is enlarged by the region C.

For example, consider a case where the flow path resistance R is small and the resistance curve is represented by the dashed-dotted line Lrl in fig. 4B. In the above case, when the pump WPA and the pump WPB are connected in parallel and the liquid is pressurized by the water pressure P3, the liquid can be discharged at the flow rate Q3.

When the path of the flow path is changed, the length of the flow path, the diameter of the flow path, and the like change in shape, and therefore the flow path resistance R changes concomitantly therewith. For example, when the flow path length is long and the flow path resistance R is large, and as a result, the resistance curve in fig. 4B changes from the one-dot chain line Lrl to the broken line Lrh, the liquid must be pressurized at the water pressure P1' in order to be discharged at the flow rate Q1. However, since the water pressure P1' is not included in any of the regions A, B, C, the liquid cannot be discharged at the flow rate Q1 by the pump WPC. That is, if the pumps are connected in parallel, the flow rate can be increased when the flow path resistance is small, but the flow rate cannot be increased when the flow path resistance is large.

On the other hand, by connecting the pumps in series, the water pressure of the liquid discharged from the pumps can be increased. Hereinafter, a case where the pumps are connected in series as described above will be described.

Fig. 5A shows a positional relationship in a case where the pump WPA and the pump WPB are arranged in series. As shown in fig. 5A, the liquid supplied to the point P _ in is pressurized by the pump WPA, then further pressurized by the pump WPB, and discharged from the point P _ out.

As in the example of fig. 4A, the pump and the water path from the point P _ in to the point P _ out can be regarded as one pump. Therefore, the pump formed by arranging the pump WPA and the pump WPB in series is referred to as a pump WPD.

The characteristics of the pump WPD as described above are as follows. First, in fig. 5A, since the pressure of the liquid is increased by both the pump WPA and the pump WPB, the water pressure PD that can be output by the pump WPD is the sum of the water pressure PA that can be output by the pump WPA and the water pressure PB that can be output by the pump WPB. That is, the relationship of PD ═ PA + PB holds. On the other hand, since the entire amount of the liquid discharged from the pump WPA flows into the pump WPB, the flow rate QD that can be discharged from the pump WPD is the same as the flow rate QA that can be discharged from the pump WPA or the flow rate QB that can be discharged from the pump WPB.

The solid line Lpd of fig. 5B is a graph showing a pump characteristic curve of the pump WPD. As described above, since the relationship of PD ═ PA + PB holds, the pump characteristic curve of the pump WPD is a curve obtained by adding the pump characteristic curve of the pump WPA (solid line Lpa) and the pump characteristic curve of the pump WPB (solid line Lpb) in the direction of the water pressure P. The range that can be output by the pump WPD is a range surrounded by the pump characteristic curve of the pump WPD, and therefore is the region a, the region B, and the region D. That is, by arranging the pump WPA and the pump WPB in series, the region in which the output can be performed is enlarged by the region D. For example, in the resistance curve of the broken line Lrh, when the pump WPA and the pump WPB are connected in series and the liquid is pressurized by the water pressure P1', the liquid can be discharged at the flow rate Q1.

On the other hand, when the flow path resistance R is small and the resistance curve is changed from the broken line Lrh to the one-dot chain line Lrl, even if the pumps are connected in series, the liquid cannot be discharged at the flow rate Q3.

As described above, when the flow path resistance R is small, the flow rate Q can be increased by connecting the pumps in parallel, and when the flow path resistance R is large, the flow rate Q can be increased by connecting the pumps in series. However, conversely, when the channel resistance R is small, the flow rate Q that can be discharged from the pump section 3 cannot be sufficiently increased even if the pumps are connected in series, and when the channel resistance R is large, the flow rate Q that can be discharged from the pump section 3 cannot be sufficiently increased even if the pumps are connected in parallel.

In embodiment 1 of the present invention, the method of connecting the plurality of pumps is switched between parallel connection and series connection according to the flow path resistance R of the cooling water path. Next, the switching of the pump will be described with reference to fig. 6 to 8.

Fig. 6 is a schematic diagram of the cooling device 100 for the internal combustion engine when the thermostat 22 is open, and fig. 7 is a schematic diagram of the cooling device 100 for the internal combustion engine when the thermostat 22 is closed. Arrows in fig. 7 and 8 indicate the direction in which the cooling water flows, solid lines indicate the state in which the cooling water flows, and broken lines indicate the state in which the cooling water does not flow.

As shown in fig. 6, since the cross-sectional area of the flow path of the heat exchange unit 2 is the sum of the cross-sectional areas of the heat exchange water path 23 and the bypass water path 24, the cooling water flows easily, and the flow path resistance Rl of the cooling water path is small. On the other hand, as shown in fig. 7, since the cross-sectional area of the flow path of the thermostat 22 is the same as the cross-sectional area of the bypass water path 24, the cooling water hardly flows, and the flow path resistance Rh of the cooling water path is large. That is, the flow resistance Rl of the cooling water path of fig. 6 is smaller than the flow resistance Rh of the cooling water path of fig. 7.

Fig. 8 is a graph showing the channel resistance R of the path of the cooling water corresponding to the switching state of the thermostat 22 and the range in which the pump section 3 can discharge corresponding to the state of the pump section 3. The resistance curve Lrl when the thermostat 22 is opened is indicated by a dashed-dotted line in fig. 8. On the other hand, a resistance curve Lrh when the thermostat 22 is closed is indicated by a broken line in fig. 8. Since the flow path resistance Rl when the thermostat 22 is opened is smaller than the flow path resistance Rh when the thermostat 22 is closed, the resistance curve Lrl is formed at a position lower than the resistance curve Lrh.

Fig. 8 shows a range in which the pumps can discharge, which can be switched between a case where a plurality of pumps are connected in parallel and a case where a plurality of pumps are connected in series. Here, in the present embodiment, a pump having the same characteristics as the pump WPA shown in fig. 4A to 5B is used as the 1 st pump 31, and a pump having the same characteristics as the pump WPB shown in fig. 4A to 5B is used as the 2 nd pump 32.

In the example shown in fig. 8, the range in which the discharge can be performed by using the 2 nd pump 32 having a capacity larger than that of the 1 st pump 31 alone is indicated by a region I. Similarly, a range in which the discharge is possible only by connecting the 1 st pump 31 and the 2 nd pump 32 in parallel is represented by a region II, and a range in which the discharge is possible only by connecting the 1 st pump 31 and the 2 nd pump 32 in series is represented by a region III. The area I is a range obtained by adding the area a and the area B in fig. 3 to 5B, the area II is a part of the area C in fig. 4B, and the area III is a part of the area D in fig. 5B.

The relationship between the switching state of the thermostat 22 and the switching state of the pump section 3 in this embodiment will be described with reference to fig. 8. First, in the present embodiment, when the thermostat 22 is switched to a state in which the cooling water flows through the heat-exchange water passage 23, the resistance curve Lrl of the path of the cooling water is indicated by a dashed-dotted line in fig. 8. In the above case, the maximum flow rate Qrl of the cooling water when the two pumps of the pump section 3 are connected in parallel is the flow rate at the intersection of the resistance curve Lrl and the pump characteristic curve Lpc when the pumps are connected in parallel. On the other hand, the maximum flow rate Qrl' of the cooling water when the two pumps of the pump section 3 are connected in series is the flow rate at the intersection of the resistance curve Lrl and the pump characteristic curve Lpb when the pumps are used alone. Here, the maximum flow rate Qrl when the two pumps are connected in parallel is larger than the maximum flow rate Qrl' when the two pumps are connected in series. That is, when the thermostat 22 is switched to a state in which the cooling water flows through the heat-exchange water passage 23, the flow rate of the cooling water can be effectively increased by connecting the two pumps in parallel.

On the other hand, in the present embodiment, when the thermostat 22 is switched to a state in which the cooling water does not flow through the heat-exchange water passage 23, the resistance curve Lrh of the path of the cooling water is indicated by a broken line in fig. 8. In the above case, the maximum flow rate Qrh' of the cooling water when the two pumps of the pump section 3 are connected in parallel is the flow rate at the intersection of the resistance curve Lrh and the pump characteristic curve Lpb when the pumps are used alone. On the other hand, the maximum flow rate Qrh of the cooling water when the two pumps of the pump section 3 are connected in series is the flow rate at the intersection of the resistance curve Lrh and the pump characteristic curve Lpd when the pumps are connected in series. Here, the maximum flow rate Qrh' when the two pumps are connected in parallel is smaller than the maximum flow rate Qrh when the two pumps are connected in series. That is, when the thermostat 22 is switched to a state in which the cooling water does not flow through the heat-exchange water passage 23, the flow rate of the cooling water can be effectively increased by connecting the two pumps in series.

As described above, when the thermostat 22 is switched so that the cooling water flows through the heat-exchange water channel 23, the two pumps of the pump unit 3 are connected in parallel, that is, the three-way valve 38 is switched to the 1 st switching position, whereby the flow rate of the cooling water can be effectively increased. On the other hand, when the thermostat 22 is switched so that the cooling water does not flow through the heat-exchange water channel 23, the two pumps of the pump unit 3 are connected in series, that is, the three-way valve 38 is switched to the 2 nd switching position, whereby the flow rate of the cooling water can be effectively increased. Therefore, in the present embodiment, whether the two pumps of the pump section 3 are connected in parallel or the two pumps of the pump section 3 are connected in series is switched depending on the switching state of the thermostat 22.

In the present embodiment, the control unit 200 determines whether or not the thermostat 22 is switched based on the water temperature Tw of the cooling water obtained by the water temperature sensor 5. For example, when the water temperature Tw obtained by the water temperature sensor 5 is equal to or higher than a preset valve opening temperature Twc of the thermostat 22, it is determined that the thermostat 22 is in a valve-opened state.

In addition to the above method, it is possible to determine whether to connect the two pumps of the pump section 3 in parallel or to connect the two pumps of the pump section 3 in series based on the channel resistance R of the path of the cooling water. An intersection x is defined as an intersection point between the pump characteristic curve when the 1 st pump 31 and the 2 nd pump 32 are connected in parallel and the pump characteristic curve when the 1 st pump 31 and the 2 nd pump 32 are connected in series. In the present embodiment, the 1 st pump 31 and the 2 nd pump 32 are connected in parallel when the flow rate Q and the water pressure P are located in a range (that is, a range in which the flow rate is high or the water pressure is low) below a resistance curve (hereinafter, a solid line Lrb in fig. 8 is referred to as a "reference resistance curve", and a flow path resistance corresponding to the resistance curve is referred to as a "reference flow path resistance Rc") passing through the intersection point x. On the other hand, if the flow rate Q and the water pressure P are located in a range above the reference resistance curve (i.e., a range where the flow rate is low or the water pressure is high), the 1 st pump 31 and the 2 nd pump 32 may be connected in series.

As described above, in embodiment 1, the cooling device 100 for an internal combustion engine includes the pump section 3 that pressure-feeds the cooling water for the internal combustion engine, and the circulation water channel including the engine water channel for the internal combustion engine, which connects the pump section 3 and the engine water channel so that the cooling water pressure-fed from the pump section 3 passes through the engine water channel for the internal combustion engine and returns to the pump section 3 again. The cooling device 100 for an internal combustion engine includes a radiator 21 (heat exchanger) that exchanges heat with coolant, and a heat exchange water passage 23 in which the radiator 21 is disposed and which is provided in parallel with a bypass water passage 24 (at least a part of a circulation water passage). The cooling device 100 for an internal combustion engine includes a thermostat 22 (water channel switching device) that switches between a state in which cooling water flows through the heat-exchange water channel 23 and a state in which cooling water does not flow through the heat-exchange water channel 23, and a control unit 200 (control device) that controls the pump unit 3.

The pump section 3 includes a 1 st pump 31, a 2 nd pump 32, and a three-way valve 38 (pump switching device) 38, and the three-way valve 38 switches between a state in which the 1 st pump 31 and the 2 nd pump 32 are connected in parallel and a state in which the 1 st pump 31 and the 2 nd pump 32 are connected in series. When the thermostat 22 is switched to a state in which the cooling water flows through the heat-exchange water passage 23 and the cooling water flows through the circulation water passage and the heat-exchange water passage 23, the control unit 200 controls the three-way valve 38 to connect the 1 st pump 31 and the 2 nd pump 32 in parallel. When the thermostat 22 is switched to a state in which the cooling water does not flow through the heat-exchange water passage 23 and the cooling water flows through only the circulation water passage, the control unit 200 controls the three-way valve 38 to connect the 1 st pump 31 and the 2 nd pump 32 in series.

When the cooling water flows through the heat exchange water passage 23 and the bypass water passage 24, the flow rate can be increased by connecting the 1 st pump 31 and the 2 nd pump 32 in parallel because the flow path resistance of the cooling water path is small. On the other hand, when the cooling water flows only in the bypass water channel 24, the flow path resistance of the cooling water path is large, and therefore, the discharge pressure of the pump unit 3 can be increased by connecting the 1 st pump 31 and the 2 nd pump 32 in series, and the flow rate of the cooling water discharged by the pump unit 3 can be increased. That is, the flow rate of the cooling water can be increased without increasing the volume of each pump of the pump section 3.

As described above, in embodiment 1, the thermostat 22 (water passage switching device) is provided in the heat-exchange water passage 23, and switches between the valve-open state and the valve-closed state in accordance with the temperature of the cooling water. The thermostat 22 allows the cooling water to flow through the heat-exchange water passage 23 when the thermostat 22 is in an open state, and stops the flow of the cooling water through the heat-exchange water passage 23 when the thermostat 22 is in a closed state.

When the thermostat 22 is in an open state, that is, when heat exchange of the cooling water is performed using the radiator 21, the pump sections 3 are connected in parallel, whereby the flow rate of the cooling water discharged from the pump sections 3 can be increased. Therefore, the heat exchange of the cooling water can be efficiently performed.

In the present embodiment, when the thermostat 22 (water path switching device) is switched to a state in which the cooling water flows through the heat-exchange water path 23 (1 st branch water path), the maximum flow rate that can be output by connecting the 1 st pump 31 and the 2 nd pump 32 in parallel by the three-way valve 38 (pump switching device) is larger than the maximum flow rate that can be output by connecting the 1 st pump 31 and the 2 nd pump 32 in series by the three-way valve 38. When the thermostat 22 is switched to a state in which the coolant does not flow through the heat-exchange water passage 23, the maximum flow rate that can be output by connecting the 1 st pump 31 and the 2 nd pump 32 in parallel by the three-way valve 38 is smaller than the maximum flow rate that can be output by connecting the 1 st pump 31 and the 2 nd pump 32 in series by the three-way valve 38.

As described above, it is advantageous to connect the pumps in parallel when a large flow of cooling water is required, and it is advantageous to connect the pumps in series when a high pressure of cooling water is required. Since the connection state of the two pumps of the pump unit 3 is switched between parallel connection and series connection according to the switching state of the thermostat 22, the flow rate of the pump can be increased while minimizing the volume of the pump.

In the present embodiment, whether the two pumps of the pump section 3 are connected in parallel or the two pumps of the pump section 3 are connected in series may be determined based on the channel resistance R of the cooling water path. That is, in the present embodiment, the circulating water path and the heat-exchange water path 23 are designed such that the flow path resistance R of the circulating water path and the heat-exchange water path 23 in the path in which the thermostat 22 is open is equal to or less than the reference flow path resistance Rc, and the flow path resistance R of the circulating water path in the path in which the thermostat 22 is closed is greater than the reference flow path resistance Rc.

In the present embodiment, the flow path resistance R of the cooling water path is compared with the reference flow path resistance Rc, but the flow path resistance R of the heat exchange unit 2 may be compared with the reference flow path resistance Rc corresponding to the heat exchange unit 2.

That is, in the present embodiment, a curve showing the relationship between the maximum flow rate and the maximum water pressure that can be output by the pump unit 3 in a state where the 1 st pump 31 and the 2 nd pump 32 are connected in parallel is referred to as a parallel characteristic curve. A curve showing the relationship between the maximum flow rate and the maximum water pressure that can be output by the pump unit 3 in a state where the 1 st pump 31 and the 2 nd pump 32 are connected in series is referred to as a series characteristic curve.

A curve showing a relationship between a flow rate and a water pressure when the flow path resistance R of the cooling water path is an arbitrary value is referred to as a resistance curve, and a flow path resistance when the resistance curve passes through an intersection x of the parallel characteristic curve and the series characteristic curve is referred to as a reference flow path resistance Rc. In this case, the circulating water path and the heat-exchange water path 23 are configured such that, when the thermostat 22 (water path switching device) is switched to a state in which the cooling water flows through the heat-exchange water path 23, the flow path resistance of the cooling water path is equal to or less than the reference flow path resistance Rc. The circulating water passage and the heat-exchange water passage 23 are configured such that, when the thermostat 22 is switched to a state in which the cooling water does not flow through the heat-exchange water passage 23, the flow path resistance of the cooling water path is greater than the reference flow path resistance Rc.

When the flow path resistance R of the cooling water path is equal to or less than the reference flow path resistance Rc, the resistance curve is as shown by the one-dot chain line Lrl in fig. 8. Therefore, by connecting the 1 st pump 31 and the 2 nd pump 32 in parallel, the amount of the cooling water discharged from the pump section 3 can be effectively increased. On the other hand, when the flow path resistance R of the cooling water path is larger than the reference flow path resistance Rc, the resistance curve is as indicated by the broken line Lrh in fig. 8, and therefore, the amount of cooling water discharged from the pump unit 3 can be effectively increased by connecting the 1 st pump 31 and the 2 nd pump 32 in series. In the case where the circulating water channel is formed as in the present embodiment, the relationship between the magnitude of the reference channel resistance Rc and the channel resistance R of the cooling water channel varies depending on the state of the thermostat 22, and therefore the discharge amount of the cooling water from the pump unit 3 can be effectively increased depending on the switching state of the pump unit 3.

In embodiment 1, the pump section 3 includes a 1 st pump 31 for pumping cooling water and a 2 nd pump 32 for pumping cooling water. The pump section 3 includes: an inlet water passage 43 into which cooling water flows; a 1 st water channel 33 in which the 1 st pump 31 is disposed; and a 2 nd water path 34 in which a 2 nd pump 32 is disposed, the 1 st water path 33 and the 2 nd water path 34 being connected to the inlet water path 43 at a branch point 35 and being disposed in parallel with each other. The pump section 3 includes: an outlet water path 44, wherein the outlet water path 44 is respectively communicated with the No. 1 water path 33 and the No. 2 water path 34 at the confluence point 36, and is used for cooling water to flow out; and an inter-pump water passage 37, the inter-pump water passage 37 communicating a water passage on the cooling water discharge side of the 1 st pump 31 in the 1 st water passage 33 with a water passage on the cooling water intake side of the 2 nd pump 32 in the 2 nd water passage 34. The pump section 3 includes a 1 st check valve 39, and the 1 st check valve 39 is disposed in the 2 nd water passage 34 between the 2 nd connection portion 372 (connection portion between the 2 nd water passage and the inter-pump water passage) and the branch point 35. The 1 st pump 31 is disposed in the 1 st water path 33 between the 1 st connection 371 (the connection between the 1 st water path and the inter-pump water path) and the branch point 35. The 2 nd pump 32 is disposed in the 2 nd water passage 34 between the 2 nd connection part 372 and the junction 36. In embodiment 1, the pump switching device is a three-way valve 38 provided at the 1 st connection 371.

The three-way valve 38 is a three-way valve configured to selectively switch between a 1 st switching position at which the coolant flowing from the 1 st water passage 33 flows directly into the 1 st water passage 33 without flowing into the inter-pump water passage 37 and a 2 nd switching position at which the coolant flowing from the 1 st water passage 33 flows into the inter-pump water passage 37 without flowing directly into the 1 st water passage 33.

The control unit 200 (control device) switches the three-way valve 38 to the 1 st switching position when the 1 st pump 31 and the 2 nd pump 32 are connected in parallel, and switches the three-way valve 38 to the 2 nd switching position when the 1 st pump 31 and the 2 nd pump 32 are connected in series.

As described above, in embodiment 1 of the present invention, the 1 st pump 31 and the 2 nd pump 32 can be switched with a simple configuration by using the three-way valve 38 and the 1 st check valve 39.

The following describes example 2 of the present invention. Fig. 9 is a schematic diagram showing a cooling apparatus for an internal combustion engine according to embodiment 2. In the cooling device of embodiment 2, a heat exchange portion 2' having a different configuration from the heat exchange portion 2 used in embodiment 1 is used. That is, in the embodiment 1, the heat exchange portion 2 is disposed on the downstream side in the flow direction of the cooling water in the engine main body 1 as shown in fig. 1, and in the embodiment 2, the engine main body 1 is disposed on the bypass water passage 24 as shown in fig. 9. In embodiment 2, a water path from the pump portion 3 to the pump portion 3 again via the bypass water path 24 and the engine water path of the engine main body 1 is referred to as a "circulation water path". Therefore, in the present embodiment, it can be said that the heat-exchange water passage 23 is provided in parallel to substantially all or all of the circulation water passages. Hereinafter, description of the portions overlapping with embodiment 1 will be omitted.

In embodiment 2, the flow path resistance R of the cooling water path also varies depending on whether the thermostat 22 is open or not. For example, when the cooling water temperature Tw is equal to or higher than the valve opening temperature Twc, the cooling water flows to both the heat-exchange water passage 23 and the bypass water passage 24 when the thermostat 22 is opened. On the other hand, when the coolant temperature Tw is less than the valve opening temperature Twc, the coolant flows only to the bypass water passage 24 when the thermostat 22 is closed. Therefore, when the thermostat 22 is opened, the cross-sectional area of the flow path of the heat exchange unit 2 'is increased, and therefore, the flow path resistance R is decreased, and when the thermostat 22 is closed, the cross-sectional area of the flow path of the heat exchange unit 2' is decreased, and therefore, the flow path resistance R is increased.

In embodiment 2, the circulating water path and the heat-exchange water path 23 are designed such that the flow path resistance R when the thermostat 22 is open is equal to or less than the flow path resistance Rc and the flow path resistance R when the thermostat 22 is closed is greater than the flow path resistance Rc. Therefore, by determining the opening and closing of the thermostat 22, it is possible to determine whether or not the flow path resistance R of the cooling water path is equal to or greater than the flow path resistance Rc. When the thermostat 22 is open, the three-way valve 38 is set to the 1 st switching position, and the 1 st pump 31 and the 2 nd pump 32 are connected in parallel, and when the thermostat 22 is closed, the three-way valve 38 is set to the 2 nd switching position, and the 1 st pump 31 and the 2 nd pump 32 are connected in series.

As described above, in embodiment 2 of the present invention, even if the engine main body 1 is disposed in the bypass water passage 24, the flow rate Q of the cooling water that can be output by the pump section 3 can be increased by switching the connection method of the 1 st pump 31 and the 2 nd pump 32 between parallel connection and series connection.

In embodiment 2 of the present invention, the engine body 1 is disposed in the bypass water passage 24, but instead of the engine body 1, a heat exchanger (for example, a heater core) through which the cooling water always flows may be disposed, and the position of the engine body 1 may be changed to another position of the circulation water passage.

Embodiment 3 of the present invention will be explained. Fig. 10 is a schematic diagram showing a cooling device for an internal combustion engine according to embodiment 3. In the cooling apparatus of the present embodiment, a heat exchange portion 2 ″ having a different configuration from the heat exchange portion 2 used in embodiment 1 is used. That is, in embodiment 3, as shown in fig. 10, the 2 nd heat exchange water passage 27 in which the EGR cooler 25 and the heat exchange on-off valve 26 are disposed is provided in parallel with the 1 st heat exchange water passage 23 and the bypass water passage 24. In embodiment 3, a water path from the pump portion 3 to the pump portion 3 via the engine water path of the engine body 1 and the bypass water path 24 is referred to as a circulation water path. Hereinafter, description overlapping with embodiment 1 will be omitted.

The EGR cooler 25 is a heat exchanger that is provided in an EGR passage for circulating exhaust gas from an exhaust pipe to an intake pipe of the internal combustion engine, and cools the temperature of the exhaust gas with cooling water. An exhaust passage through which exhaust gas flows and a cooling water passage through which cooling water flows are arranged inside the EGR cooler 25 via fins (fin), and the temperature of the exhaust gas is lowered by capturing heat of the exhaust gas with the cooling water.

The heat exchange on-off valve 26 is disposed downstream of the EGR cooler 25, and is capable of selectively switching between a state in which the coolant flows through the EGR cooler 25 and the 2 nd heat exchange water passage 27 (a state in which the valve is opened) and a state in which the coolant does not flow through the EGR cooler 25 and the 2 nd heat exchange water passage 27 (a state in which the valve is closed). In the present embodiment, the heat exchange on-off valve 26 is controlled in response to a signal from the control unit 200.

In embodiment 3, since the thermostat 22 and the heat exchange on-off valve 26 have two states, i.e., an open valve state and a closed valve state, there are 4 paths for the cooling water. When both the thermostat 22 and the heat exchange on-off valve 26 are in the open state, the water path switching device is switched to the state in which the cooling water flows through the heat exchange water path, and the flow path resistance of the cooling water path is the smallest of 4, so the 1 st pump 31 and the 2 nd pump 32 are connected in parallel. When both the thermostat 22 and the heat exchange on-off valve 26 are in the closed state, the water path switching device is switched to a state in which the cooling water does not flow through the heat exchange water path, and the flow path resistance of the cooling water path is the maximum of 4, so the 1 st pump 31 and the 2 nd pump 32 are connected in series. However, when only one of the thermostat 22 and the heat exchange on-off valve 26 is in the open state, the flow path resistance of the cooling water path is moderate, and therefore it is difficult to determine the method of connecting the 1 st pump 31 and the 2 nd pump 32.

In the present embodiment, the control unit 200 determines the method of connecting the pumps by determining whether the requested flow rate Q _ t and the requested water pressure P _ t for the pump unit 3 are included in any one of the regions I to III in fig. 8. That is, when the demanded flow rate Q _ t and the demanded water pressure P _ t are included in the region I, the control unit 200 controls the three-way valve 38 to drive a single pump while connecting the two pumps of the pump section 3 in parallel. When the requested flow rate Q _ t and the requested water pressure P _ t are included in the region II, the control unit 200 drives both the pumps while connecting both the pumps of the pump unit 3 in parallel, and when the requested flow rate Q _ t and the requested water pressure P _ t are included in the region III, controls the three-way valve 38 to connect both the pumps in series. For example, the thermostat 22 is opened, the heat exchange on-off valve 26 is closed, and the requested flow rate Q _ t and the requested water pressure P _ t to the pump unit 3 are included in the region II. In the above case, the 1 st pump 31 and the 2 nd pump 32 are connected in parallel. On the other hand, the thermostat 22 is in a closed state, the heat exchange on-off valve 26 is in an open state, and the requested flow rate Q _ t and the requested water pressure P _ t to the pump unit 3 are included in the region III. In the above case, the 1 st pump 31 and the 2 nd pump 32 are connected in series.

In embodiment 3, the control unit 200 may store a method of connecting the two pumps of the pump section 3 with respect to the state of the thermostat 22 and the state of the heat exchange on-off valve 26. For example, the control unit 200 may store the following: the pumps are connected in parallel only when the thermostat 22 and the heat exchange on-off valve 26 are in the open state, and otherwise the pumps are connected in series, and the connection method of the 1 st pump 31 and the 2 nd pump 32 is switched in accordance with the states of the thermostat 22 and the heat exchange on-off valve 26.

In embodiment 3, the flow path resistance R may be measured in advance for each cooling water path and compared with the reference flow path resistance Rc. That is, the 1 st pump 31 and the 2 nd pump 32 may be connected in parallel when the flow path resistance R of the cooling water path measured in advance is equal to or less than the reference flow path resistance Rc, and the 1 st pump 31 and the 2 nd pump 32 may be connected in series when the flow path resistance R of the cooling water path is greater than the reference flow path resistance Rc.

As described above, according to the present embodiment, the heat exchanger includes the radiator 21 (1 st heat exchanger) and the EGR cooler 25 (2 nd heat exchanger). The heat-exchange water passage includes a 1 st heat-exchange water passage 23 in which the radiator 21 is disposed and which is provided in parallel with at least a part of the circulating water passage, and a 2 nd heat-exchange water passage 27 in which the EGR cooler 25 is disposed and which is provided in parallel with at least a part of the circulating water passage. The water path switching device includes a thermostat 22 (1 st water path switching device) that switches between a state in which the coolant flows through the 1 st heat-exchange water path 23 and a state in which the coolant does not flow through the 1 st heat-exchange water path 23, and a heat-exchange on-off valve 26 (2 nd water path switching device) that switches between a state in which the coolant flows through the 2 nd heat-exchange water path 27 and a state in which the coolant does not flow through the 2 nd heat-exchange water path 27.

In the present embodiment, when the water path switching device is switched to the state in which the cooling water flows through the heat-exchange water path, the thermostat 22 is switched to the state in which the cooling water flows through the 1 st heat-exchange water path 23, and the heat-exchange on-off valve 26 is switched to the state in which the cooling water flows through the 2 nd heat-exchange water path 27. Therefore, in the present embodiment, the control unit 200 (control device) connects the 1 st pump and the 2 nd pump in parallel when the thermostat 22 and the heat exchange on-off valve 26 are switched to the state in which the coolant flows through both the 1 st heat exchange water passage 23 and the 2 nd heat exchange water passage 27.

In the present embodiment, the water path switching device is switched to the state in which the cooling water does not flow through the heat-exchange water path, and the thermostat 22 is switched to the state in which the cooling water does not flow through the 1 st heat-exchange water path 23 and the heat-exchange on-off valve 26 is switched to the state in which the cooling water does not flow through the 2 nd heat-exchange water path 27. Therefore, in the present embodiment, the control unit 200 connects the 1 st pump and the 2 nd pump in series when the thermostat 22 and the heat exchange on-off valve 26 are switched to a state in which the coolant does not flow through both the 1 st heat-exchange water passage 23 and the 2 nd heat-exchange water passage 27.

The control unit 200 (control device) stores, as the region II (1 st region), a region of flow rate and water pressure that can be output only by connecting the 1 st pump 31 and the 2 nd pump 32 in parallel when the thermostat 22 and the heat-exchange on-off valve 26 are switched to a state in which the coolant flows in either the 1 st heat-exchange water path 23 or the 2 nd heat-exchange water path 27. The control unit 200 stores, as the zone III (zone 2), a zone of the flow rate Q _ t and the water pressure P _ t that can be output only by connecting the 1 st pump 31 and the 2 nd pump 32 in series when the thermostat 22 and the heat-exchange on-off valve 26 are switched to the state in which the coolant flows in either the 1 st heat-exchange water path 23 or the 2 nd heat-exchange water path 27. The control unit 200 calculates a required flow rate Q _ t to the pump section 3 and a required water pressure P _ t to the pump section, which is determined by the required flow rate Q _ t, the state of the thermostat 22, and the state of the heat exchange on-off valve 26. When the required flow rate Q _ t and the required water pressure P _ t are included in the region II, the control unit 200 controls the three-way valve 38 (pump switching device) to connect the 1 st pump 31 and the 2 nd pump 32 in parallel. On the other hand, when the requested flow rate Q _ t and the requested water pressure P _ t are included in the region III, the control unit 200 controls the three-way valve 38 to connect the 1 st pump 31 and the 2 nd pump 32 in series.

According to the embodiment, whether the 1 st pump 31 and the 2 nd pump 32 are connected in parallel or the 1 st pump 31 and the 2 nd pump 32 are connected in series is determined based on the required flow rate Q _ t and the required water pressure P _ t of the pump section, which are determined in accordance with the path of the cooling water. Therefore, even when the number of the cooling water paths is 3 or more, it is possible to accurately determine whether the cooling water paths should be connected in parallel or in series.

The invention of example 4 will be explained. Fig. 11 is a schematic diagram showing a cooling apparatus for an internal combustion engine according to embodiment 4. In the cooling device according to embodiment 1, as shown in fig. 1, the heat exchange portion 2 is disposed only on the downstream side in the flow direction of the cooling water of the engine body 1. In contrast, in embodiment 4, as shown in fig. 11, the 2 nd heat exchange unit 2' ″ is disposed on the upstream side in the flow direction of the cooling water in the engine body 1, and the heat exchange unit 2 is disposed on the downstream side in the flow direction of the cooling water. In the present embodiment, a water channel in which the cooling water discharged from the pump portion 3 is recirculated to the pump portion 3 via the 2 nd bypass water channel 28, the engine water channel of the engine main body 1, and the 1 st bypass water channel 24 is referred to as a circulation water channel.

The 2 nd heat exchange unit 2' ″ is a device for exchanging heat between the cooling water and the exhaust gas. In the present embodiment, the 2 nd heat exchange unit 2' ″ includes the EGR cooler 25, the heat exchange on-off valve 26, the 2 nd heat exchange water passage 27, and the 2 nd bypass water passage 28. The EGR cooler 25 and the heat exchange on-off valve 26 are provided in the 2 nd heat exchange water passage 27, and the 2 nd bypass water passage 28 is provided so as to bypass the EGR cooler 25 and the heat exchange on-off valve 26.

When the heat exchange on-off valve 26 is opened, the cooling water flows through the 2 nd heat exchange water passage 27 and the 2 nd bypass water passage 28, so that the cross-sectional area of the passage of the 2 nd heat exchange unit 2' ″ is increased, and the passage resistance R of the passage of the cooling water is small. On the other hand, when the heat exchange on-off valve 26 is closed, the cooling water flows only through the 2 nd bypass water passage 28, so that the cross-sectional area of the flow passage of the 2 nd heat exchange unit 2 ″, and the flow passage resistance R of the flow passage of the cooling water becomes large.

In embodiment 4, the flow path resistance R relating to the path of the cooling water from the confluence point 36 to the branch point 35 is determined by both the open/closed state of the thermostat 22 of the heat exchange unit 2 and the open/closed state of the heat exchange on-off valve 26 of the 2 nd heat exchange unit 2 ″. In the present embodiment, as in embodiment 3, when both the thermostat 22 and the heat-exchange on-off valve 26 are in the open state, the water path switching device is switched to the state in which the cooling water flows through the heat-exchange water path, and the 1 st pump 31 and the 2 nd pump 32 are connected in parallel. When both the thermostat 22 and the heat exchange on-off valve 26 are in the closed state, the water path switching device is switched to a state in which the cooling water does not flow through the heat exchange water path, and the 1 st pump 31 and the 2 nd pump 32 are connected in series. The method of connecting the pumps is determined by determining whether or not the required flow rate Q _ t and the required water pressure P _ t for the pump unit 3 are included in any one of the regions I to III in fig. 8.

In the present embodiment, the EGR cooler 25 is used as the heat exchanger of the 2 nd heat exchange unit 2 '″, but the heat exchanger of the 2 nd heat exchange unit 2' ″ may be a heat exchanger for other applications such as a heater core for exchanging heat between air in the vehicle and cooling water.

The 5 th embodiment of the present invention will be explained. Fig. 12 is a schematic diagram showing a cooling apparatus for an internal combustion engine according to embodiment 5. In the cooling device of the present embodiment, a pump section 3' having a different configuration from the pump section 3 used in embodiment 1 is used. Hereinafter, description overlapping with embodiment 1 will be omitted.

As is clear from comparison between fig. 1 and 12, the pump section 3' of embodiment 5 includes an on-off valve 41 instead of the three-way valve 38 shown in fig. 1. In the present embodiment, a 2 nd check valve 40 is provided in addition to a check valve (hereinafter, referred to as "1 st check valve" in the present embodiment) 39 disposed in the 2 nd water passage 34. In embodiment 1, the three-way valve 38 controls the flow of the cooling water in the inter-pump water passage 37, but in embodiment 5, the on-off valve 41 controls the flow of the cooling water in the inter-pump water passage 37.

The 2 nd check valve 40 is a valve for allowing the cooling water to flow in one direction. In the present embodiment, the 2 nd check valve 40 is disposed in the 1 st water passage 33 between the 1 st connection portion 371 and the confluence point 36. The 2 nd check valve 40 is configured to allow the coolant flowing from the 1 st connection part 371 toward the junction 36 to flow therethrough, but to prohibit the coolant flowing from the junction 36 toward the 2 nd connection part 372 from flowing therethrough.

The on-off valve 41 is provided in the inter-pump water passage 37 and is switchable between a 1 st switching position for closing the inter-pump water passage 37 and a 2 nd switching position for opening the inter-pump water passage 37. Therefore, when the on-off valve 41 is at the 1 st switching position, the cooling water flowing into the 1 st connection portion 371 does not flow to the 2 nd connection portion 372, while when the on-off valve 41 is at the 2 nd switching position, the cooling water flowing into the 1 st connection portion 371 flows to the 2 nd connection portion 372. The opening/closing valve 41 is controlled by receiving a signal from the control unit 200.

In embodiment 5, by controlling the open/close valve 41 between the 1 st switching position and the 2 nd switching position, it is possible to switch between a case where the 1 st pump 31 and the 2 nd pump 32 are connected in series and a case where the 1 st pump 31 and the 2 nd pump 32 are connected in parallel.

Specifically, when the on-off valve 41 is switched to the 1 st switching position, the 1 st pump 31 and the 2 nd pump 32 are connected in parallel because the flow of the cooling water to the inter-pump water passage 37 is blocked.

On the other hand, when the on-off valve 41 is switched to the 2 nd switching position, the 1 st pump 31 and the 2 nd pump 32 are connected in series because the flow of the cooling water in the inter-pump water passage 37 is permitted. When the 1 st pump 31 and the 2 nd pump 32 are connected in series, the flow of the cooling water from the 1 st connection part 371 toward the confluence point 36 via the 1 st water channel 33 is restricted by the 2 nd check valve 40, so that the cooling water discharged from the 2 nd pump 32 does not flow back toward the 1 st connection part 371.

The cooling apparatus of embodiment 5 is controlled in the same manner as the cooling apparatus of embodiment 1. That is, when the cooling water temperature Tw is equal to or higher than the valve opening temperature Twc and the thermostat 22 is open, the opening/closing valve 41 is controlled to the 1 st switching position because the flow resistance R is equal to or lower than the reference flow resistance Rc. As a result, since the coolant does not flow through the inter-pump water passage 37, the 1 st pump 31 and the 2 nd pump 32 are connected in parallel. On the other hand, when the cooling water temperature Tw is less than the valve opening temperature Twc and the thermostat 22 is closed, the opening/closing valve 41 is controlled to the 2 nd switching position because the flow path resistance R is greater than the reference flow path resistance Rc. As a result, since the cooling water flows through the inter-pump water passage 37, the 1 st pump 31 and the 2 nd pump 32 are connected in series.

As described above, in embodiment 5 of the present invention, the pump section 3' includes the 1 st pump 31 for pumping the cooling water and the 2 nd pump 32 for pumping the cooling water. The pump section 3' includes an inlet water passage 43 into which cooling water flows, a 1 st water passage 33 in which the 1 st pump 31 is disposed and a 2 nd water passage 34 in which the 2 nd pump 32 is disposed, the 1 st water passage 33 communicating with the inlet water passage 43 at a branch point 35 and being disposed in parallel with each other. The pump unit 3' includes an outlet water passage 44 that communicates with the 1 st water passage 33 and the 2 nd water passage 34 at the merging point 36, and that allows the cooling water to flow out, and an inter-pump water passage 37 that communicates a water passage on the cooling water discharge side of the 1 st pump 31 in the 1 st water passage 33 with a water passage on the cooling water suction side of the 2 nd pump 32 in the 2 nd water passage 34. The pump unit 3' further includes a 1 st check valve 39 disposed in the 2 nd water path 34 between the 2 nd connection portion 372 (connection portion between the 2 nd water path and the inter-pump water path) and the branch point 35, a 2 nd check valve 40 disposed in the 1 st water path 33 between the 1 st connection portion 371 (connection portion between the 1 st water path and the inter-pump water path) and the junction point 36, and an on-off valve 41 (pump switching device) provided in the inter-pump water path 37. The 1 st pump 31 is disposed in the 1 st water path 33 between the 1 st connection portion 371 and the branch point 35, and the 2 nd pump 32 is disposed in the 2 nd water path 34 between the 2 nd connection portion 372 and the junction 36. The pump switching device is an on-off valve 41 provided in the inter-pump water passage 37, and is switchable between a 1 st switching position for closing the inter-pump water passage 37 and a 2 nd switching position for opening the inter-pump water passage 37.

The control unit 200 (control device) sets the on-off valve 41 to the 1 st switching position when the 1 st pump 31 (1 st pump) and the 2 nd pump 32 (2 nd pump) are connected in parallel, and sets the on-off valve 41 to the 2 nd switching position when the 1 st pump 31 and the 2 nd pump 32 are connected in series.

In the 5 th embodiment of the present invention as described above, the parallel connection or the series connection of the 1 st pump 31 and the 2 nd pump 32 can be switched by a simple configuration by using the on-off valve 41.

A plurality of specific control methods in the cooling device for an internal combustion engine according to the above embodiments will be described.

First, the 1 st control method will be explained. The present control method can be applied to all of the embodiments 1 to 5 described above. Hereinafter, a case where the present embodiment is applied to example 1 will be representatively described. Fig. 13 is a flowchart showing a routine for controlling the pump related to the 1 st control example. This routine is repeatedly executed at a certain cycle.

In step S101, the control unit 200 calculates a required flow rate for the pump. Specifically, in the present control method, the control unit 200 calculates the degree of cooling of the engine body 1 based on the engine load. For example, the higher the engine load, the higher the temperature of the engine body 1. Therefore, in order to set the temperature of the engine body 1 to the target temperature, the flow rate of the cooling water must be increased as the engine load is increased. Therefore, the required flow rate Q _ t, which is the target value of the flow rate of the cooling water, is calculated based on the engine load.

In step S102, the control unit 200 measures the cooling water temperature Tw using the water temperature sensor 5. In step S103, the control unit 200 determines whether or not the cooling water temperature Tw is equal to or higher than the valve opening temperature Twc. In the present control example, the valve opening temperature Twc is a temperature at which the thermostat 22 opens. When the control unit 200 determines that the cooling water temperature Tw is equal to or higher than the valve opening temperature Twc and the thermostat 22 is opened, the flow resistance R is equal to or lower than the reference flow resistance Rc, and the control routine proceeds to step S104 to connect the 1 st pump 31 and the 2 nd pump 32 in parallel. On the other hand, when the control unit 200 determines that the cooling water temperature Tw is less than the valve opening temperature Twc and the thermostat 22 is closed, the control routine proceeds to step S108 to determine that the flow resistance R is less than the reference flow resistance Rc and to connect the 1 st pump 31 and the 2 nd pump 32 in series.

In step S104, the control unit 200 outputs a signal for setting the three-way valve 38 to the 1 st switching position. When the three-way valve 38 receives a signal from the control unit 200, the inter-pump water passage 37 is closed. As a result, the cooling water discharged from the 1 st pump 31 is caused to flow directly into the 1 st water passage 33 without flowing into the inter-pump water passage 37. Therefore, the 1 st pump 31 and the 2 nd pump 32 are connected in parallel.

In step S105, the control unit 200 calculates a requested water pressure P _ t, which is a target water pressure, for causing the pump unit 3 to discharge the requested flow rate Q _ t. In the present control method, the control unit 200 stores in advance a resistance curve when the thermostat 22 is opened, and the control unit 200 calculates the required water pressure P _ t by applying the required flow rate Q _ t to the resistance curve.

In step S106, the control unit 200 calculates a 1 st requested water pressure P1_ t, which is a target water pressure of the 1 st pump 31, and a 2 nd requested water pressure P2_ t, which is a target water pressure of the 2 nd pump 32, based on the requested water pressure P _ t. In the present control method, since the 1 st pump 31 and the 2 nd pump 32 are arranged in parallel, the control unit 200 sets the 1 st and 2 nd required water pressures P1_ t and P2_ t as the required water pressure P _ t.

In step S107, the control unit 200 controls the 1 st pump 31 and the 2 nd pump 32 such that the water pressure of the cooling water discharged from the 1 st pump 31 becomes the 1 st required water pressure P1_ t and the water pressure of the cooling water discharged from the 2 nd pump 32 becomes the 2 nd required water pressure P2_ t. When the control unit 200 ends the processing of step S107, the processing of the present routine ends. On the other hand, in step S103, when the cooling water temperature Tw is less than the valve opening temperature Twc, the control routine proceeds to step S108.

In step S108, the control unit 200 outputs a signal for setting the three-way valve 38 to the 2 nd switching position. When the three-way valve 38 receives a signal from the control unit 200, the inter-pump water passage 37 is opened, and the water passage through which the cooling water flows from the three-way valve 38 to the junction 36 via the 1 st water passage 33 is closed. Therefore, the 1 st pump 31 and the 2 nd pump 32 are connected in series.

In step S109, the control unit 200 calculates a requested water pressure P _ t, which is a target water pressure, for causing the pump unit 3 to discharge the requested flow rate Q _ t. In the present control method, the control unit 200 stores in advance a resistance curve when the thermostat 22 is closed, and the control unit 200 calculates the required water pressure P _ t by applying the required flow rate Q _ t to the resistance curve.

In step S110, the control unit 200 calculates a 1 st requested water pressure P1_ t, which is a target water pressure of the 1 st pump 31, and a 2 nd requested water pressure P2_ t, which is a target water pressure of the 2 nd pump 32, based on the requested water pressure P _ t. In the present control method, since the 1 st pump 31 and the 2 nd pump 32 are arranged in series, the control unit 200 sets the 1 st required water pressure P1_ t and the 2 nd required water pressure P2_ t such that the pressure obtained by summing the 1 st required water pressure P1_ t and the 2 nd required water pressure P2_ t becomes the required water pressure P _ t. When the control unit 200 ends the processing of step S110, the process proceeds to step S107, and the control unit 200 controls the 1 st pump 31 and the 2 nd pump 32, and ends the processing of the present routine.

As described above, in embodiment 1 of the present invention, the control unit 200 indirectly measures the flow path resistance R by measuring the cooling water temperature Tw, and switches between the series connection and the parallel connection of the 1 st pump 31 and the 2 nd pump 32 according to the cooling water temperature Tw. When the flow path resistance R is small, the 1 st pump 31 and the 2 nd pump 32 are connected in parallel, whereby the flow rate can be increased as compared with the case where the pumps are connected individually or in series. On the other hand, when the flow path resistance R is large, the 1 st pump 31 and the 2 nd pump 32 are connected in series, whereby the flow rate can be increased as compared with the case where the pumps are connected individually or in parallel.

A method 2 for controlling the cooling device for an internal combustion engine according to each of the above embodiments will be described. The present control method can be applied to all of the embodiments 1 to 5 described above. Hereinafter, a case where the present embodiment is applied to example 1 will be representatively described.

In the case where the required flow rate Q _ t is sufficiently small and the required flow rate Q _ t can be discharged by a single pump, the 2 nd control method uses only one of the 1 st pump 31 and the 2 nd pump 32. Hereinafter, the flow rate for determining whether or not the discharge can be performed by using a single pump is referred to as "switching flow rate Qc".

The switching flow rate Qc is briefly described with reference to fig. 14. Fig. 14 is a schematic diagram showing a change in the pump connection method in the 2 nd control method. In the present control method, the switching flow rate Qc is set to the flow rate Q that can be discharged using a single pump when the flow path resistance R is assumed to be the maximum, that is, when the resistance curve is the broken line Lrh in fig. 14. In this case, the region where the flow rate is less than the switching flow rate Qc becomes a region (region I') where the single pump operation is possible. In the present control method, even in a region where the flow rate is more than the switching flow rate Qc, the cooling water is discharged using a plurality of pumps, even in a case where the treatment is possible with a single pump. For example, a region where the flow rate is larger than the switching flow rate Qc and the flow rate is larger than the resistance curve of the reference flow path resistance Rc is a region (region II ') where the 1 st pump 31 and the 2 nd pump 32 are connected in parallel, and a region where the flow rate is larger than the switching flow rate Qc and the flow rate is smaller than the resistance curve of the reference flow path resistance Rc is a region (region III') where the 1 st pump 31 and the 2 nd pump 32 are connected in series.

Fig. 15 is a flowchart showing a routine for controlling the pump, which is related to the 2 nd control method. This routine is repeatedly executed at a certain cycle.

In step S101, the control unit 200 calculates the required flow rate Q _ t, and the control routine proceeds to step S201.

In step S201, the control unit 200 determines whether or not the requested flow rate Q _ t is larger than the switching flow rate Q _ c. When the required flow rate Q _ t is larger than the switching flow rate Q _ c, the control routine proceeds to step S102 in order to discharge the cooling water using the plurality of pumps. The processing from step S102 onward is the same as the 1 st control method, and therefore, the description thereof is omitted. On the other hand, when the required flow rate Q _ t is equal to or less than the switching flow rate Q _ c, the control routine proceeds to step S202 in order to discharge the cooling water using a single pump.

In step S202, the control unit 200 outputs a signal for setting the three-way valve 38 to the 1 st switching position. When the three-way valve 38 receives a signal from the control unit 200, the inter-pump water passage 37 is closed. As a result, the cooling water discharged from the 1 st pump 31 flows directly into the 1 st water passage 33 without flowing into the inter-pump water passage 37. Therefore, the 1 st pump 31 and the 2 nd pump 32 are connected in parallel. The reason why the 1 st pump 31 and the 2 nd pump 32 are connected in parallel as described above is that one of these pumps cannot be used alone unless they are connected in parallel. This is because, when the 1 st pump 31 and the 2 nd pump 32 are connected in series, if either one of the 1 st pump 31 and the 2 nd pump 32 is stopped, the cooling water does not flow.

In step S203, the control unit 200 calculates a requested water pressure P _ t, which is a target water pressure, for causing the pump unit 3 to discharge the requested flow rate Q _ t.

In step S204, the control unit 200 calculates a 1 st requested water pressure P1_ t, which is a target water pressure of the 1 st pump 31, and a 2 nd requested water pressure P2_ t, which is a target water pressure of the 2 nd pump 32, based on the requested water pressure P _ t. In the present control method, either one of the 1 st pump 31 and the 2 nd pump 32 is driven. For example, in the case of driving only the 1 st pump 31, the control unit 200 sets the 1 st required water pressure P1_ t as the required water pressure P _ t and the 2 nd required water pressure P2_ t as 0. That is, only the 1 st pump 31 is driven, and the 2 nd pump 32 is not driven. When the process of step S204 ends, the control routine proceeds to step S107, and the control unit 200 controls the 1 st pump 31 and the 2 nd pump 32, and ends the process of the present routine.

When the required flow rate Q _ t of the pump unit 3 is smaller than the switching flow rate Qc (preset flow rate), the control unit 200 (control device) controls the three-way valve 38 (pump switching device) to connect the 1 st pump 31 and the 2 nd pump 32 in parallel and to drive only one of the 1 st pump 31 and the 2 nd pump 32, regardless of the state of the thermostat 22 (water path switching device).

According to the above-described control method 2, as compared with the case where a plurality of pumps are always used, a period in which one pump is not used can be secured, and therefore, the consumption of the pump can be suppressed.

A 3 rd control method of the cooling device for an internal combustion engine according to each of the above embodiments will be described. The present control method can be applied to all of the embodiments 1 to 5 described above. Hereinafter, a case where the present embodiment is applied to example 4 will be representatively described. Fig. 16 is a flowchart showing a routine for controlling the pump, which is related to the 3 rd control method. This routine is repeatedly executed at a certain cycle.

In the 2 nd control method, the required water pressure P _ t is calculated after determining whether the 1 st pump 31 and the 2 nd pump 32 are connected in parallel or the 1 st pump 31 and the 2 nd pump 32 are connected in series. In contrast, in the present 3 rd control method, after the required flow rate Q _ t and the required water pressure P _ t are calculated, whether the 1 st pump 31 and the 2 nd pump 32 are connected in parallel or the 1 st pump 31 and the 2 nd pump 32 are connected in series is set.

In step S101, after the control unit 200 calculates the required flow rate Q _ t, the control routine proceeds to step S301.

In step S301, the control unit 200 calculates the flow path resistance R. In the present control method, first, the control unit 200 detects the open/close states of the thermostat 22 and the heat exchange on-off valve 26. For example, in the same manner as step S103, the control unit 200 determines the open/close state of the thermostat 22 based on the cooling water temperature Tw acquired by the water temperature sensor 5. The control unit 200 determines the open/close state of the heat exchange on/off valve 26 by checking the signal sent from the control unit 200 to the heat exchange on/off valve 26.

The control unit 200 calculates the flow path resistance R corresponding to the open/close state of the thermostat 22 and the heat exchange on-off valve 26. For example, the control unit 200 reads the flow path resistance R of the path of the cooling water corresponding to the open/close state of the thermostat 22 and the open/close state of the heat exchange on-off valve 26 recorded in the control unit 200, thereby calculating the flow path resistance R.

In step S302, the control unit 200 calculates the required water pressure P _ t of the pump unit 3, for example, because P _ t is R × Q _ t²Since the relationship of (1) is established, the present control method calculates P _ t using the required flow rate Q _ t and the flow path resistance R based on the relationship.

Here, in the present control method, the control unit 200 stores a map in which a pump connection method corresponding to the required flow rate Q _ t and the required water pressure P _ t is set as shown in fig. 8.

In step S303, the control unit 200 determines whether the pump alone can be used by determining whether the required flow rate Q _ t and the required water pressure P _ t are included in the region I in fig. 8. When the required flow rate Q _ t and the required water pressure P _ t are included in the region I, the control routine proceeds to step S203 in order to drive the pump alone. The processing from step S203 onward is the same as steps S203 and S205 of the 2 nd control method except that step S204 is omitted, and therefore, the description thereof is omitted. If the required flow rate Q _ t and the required water pressure P _ t are not included in the region I, the control routine proceeds to step S304.

In step S304, the control unit 200 determines whether or not the pumps are connected in parallel by determining whether or not the requested flow rate Q _ t and the requested water pressure P _ t are included in the region II in fig. 8. When the required flow rate Q _ t and the required water pressure P _ t are included in the region II, the control routine proceeds to step S104 in order to connect the pumps in parallel. The processing from step S104 onward is the same as the 1 st control method except that step S105 is omitted, and therefore, the description thereof is omitted. If the required flow rate Q _ t and the required water pressure P _ t are not included in the region II, the control routine proceeds to step S305.

In step S305, the control unit 200 determines whether or not the pumps are connected in series by determining whether or not the requested flow rate Q _ t and the requested water pressure P _ t are included in the region III in fig. 8. When the required flow rate Q _ t and the required water pressure P _ t are included in the region III, the control routine proceeds to step S108 to connect the pumps in series. The processing from step S108 onward is the same as the 1 st control method except that step S109 is omitted, and therefore, the description thereof is omitted. When the required flow rate Q _ t and the required water pressure P _ t are not included in the region III, the control unit 200 ends the processing of this routine. The performance of the pump and the cooling circuit are designed so that a required amount of cooling water can be supplied even under the most severe conditions for cooling the engine body 1. Therefore, normally, in step S305, the required flow rate Q _ t and the required water pressure P _ t are included in the region III. Therefore, in step S305, when the required flow rate Q _ t and the required water pressure P _ t are not included in the region III, the control unit 200 may determine that there is an abnormality and perform a process for dealing with the abnormality.

Claims (16)

1. A cooling device for an internal combustion engine, comprising:

a pump section that pressure-feeds cooling water of the internal combustion engine;

a circulation water channel including an engine water channel of the internal combustion engine, the circulation water channel being configured to connect the pump portion and the engine water channel such that the cooling water pumped from the pump portion passes through the engine water channel and returns to the pump portion again;

a heat exchanger configured to exchange heat with cooling water;

a heat-exchange water path in which the heat exchanger is disposed, the heat-exchange water path being provided in parallel with at least a part of the circulation water path;

a water passage switching device that switches between a state in which cooling water flows through the heat exchange water passage and a state in which cooling water does not flow through the heat exchange water passage; and

a control device that controls the pump section,

wherein the content of the first and second substances,

the pump section includes a 1 st pump, a 2 nd pump, and a pump switching device that switches between a state in which the 1 st pump and the 2 nd pump are connected in parallel and a state in which the 1 st pump and the 2 nd pump are connected in series,

the control device is configured to control the pump switching device to connect the 1 st pump and the 2 nd pump in parallel when the water path switching device is switched to a state in which the cooling water flows in the heat exchange water path and the cooling water flows in the circulation water path and the heat exchange water path,

the control device is configured to control the pump switching device to connect the 1 st pump and the 2 nd pump in series when the water channel switching device is switched to a state in which the cooling water does not flow in the heat exchange water channel and the cooling water flows only in the circulation water channel,

the pump section includes a 1 st pump for feeding cooling water under pressure, a 2 nd pump for feeding cooling water under pressure, an inlet water channel into which cooling water flows, an outlet water channel from which cooling water flows, a 1 st water channel in which the 1 st pump is disposed, a 2 nd water channel in which the 2 nd pump is disposed, an inter-pump water channel, and a check valve;

the 1 st waterway and the 2 nd waterway are communicated with the inlet waterway at branch points, are arranged in parallel with each other and are communicated with the outlet waterway at confluence points;

the inter-pump water passage communicates a water passage on a cooling water discharge side of the 1 st pump in the 1 st water passage with a water passage on a cooling water suction side of the 2 nd pump in the 2 nd water passage;

the check valve is disposed in the 2 nd water path between a connection portion of the 2 nd water path and the inter-pump water path and the branch point;

the pump switching device is a three-way valve arranged at the connecting part of the No. 1 water channel and the water channel between the pumps;

the three-way valve is configured to selectively switch between a 1 st switching position and a 2 nd switching position, the 1 st switching position being a switching position at which the cooling water flowing in the 1 st water path flows directly into the 1 st water path without flowing into the inter-pump water path, and the 2 nd switching position being a switching position at which the cooling water flowing in the 1 st water path flows into the inter-pump water path without flowing directly into the 1 st water path; and the number of the first and second electrodes,

the control device is configured to switch the three-way valve to the 1 st switching position when the 1 st pump and the 2 nd pump are connected in parallel, and to switch the three-way valve to the 2 nd switching position when the 1 st pump and the 2 nd pump are connected in series.

2. The cooling apparatus of an internal combustion engine according to claim 1,

the water path switching device is a thermostat which is arranged in the heat exchange water path and switches a valve opening state and a valve closing state according to the water temperature of cooling water;

the thermostat is configured such that cooling water flows through the heat exchange water passage when the thermostat is in an open state; and the number of the first and second electrodes,

the thermostat is configured to stop the flow of the cooling water to the heat exchange water passage when the thermostat is in a closed state.

3. The cooling apparatus of an internal combustion engine according to claim 1,

when the water channel switching device is switched to a state in which the cooling water flows in the heat exchange water channel, the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in parallel is larger than the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in series; and the number of the first and second electrodes,

when the water channel switching device is switched to a state in which the cooling water does not flow in the heat-exchange water channel, the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in parallel is smaller than the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in series.

4. The cooling apparatus of an internal combustion engine according to claim 2,

when the water channel switching device is switched to a state in which the cooling water flows in the heat exchange water channel, the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in parallel is larger than the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in series; and the number of the first and second electrodes,

when the water channel switching device is switched to a state in which the cooling water does not flow in the heat-exchange water channel, the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in parallel is smaller than the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in series.

5. The cooling apparatus of an internal combustion engine according to claim 1,

the circulation water path and the heat-exchange water path are configured such that when the water path switching device is switched to a state in which cooling water flows in the heat-exchange water path, a flow path resistance of the cooling water path is equal to or less than a reference flow path resistance, and when the water path switching device is switched to a state in which cooling water does not flow in the heat-exchange water path, the flow path resistance of the cooling water path is greater than the reference flow path resistance;

when a curve showing a relationship between a flow rate and a water pressure when a flow path resistance of the cooling water path is an arbitrary value is defined as a resistance curve, the reference flow path resistance is a flow path resistance when the resistance curve passes through an intersection of a parallel characteristic curve and a series characteristic curve;

the parallel characteristic curve is a curve showing a relationship between a maximum flow rate and a maximum water pressure that can be output by the pump section in a state where the 1 st pump and the 2 nd pump are connected in parallel; and the number of the first and second electrodes,

the series characteristic curve is a curve showing a relationship between a maximum flow rate that the pump section can output and a maximum water pressure in a state where the 1 st pump and the 2 nd pump are connected in series.

6. The cooling apparatus of an internal combustion engine according to any one of claims 1 to 5,

the control device is configured to control the pump switching device to connect the 1 st pump and the 2 nd pump in parallel and to drive only one of the 1 st pump and the 2 nd pump regardless of a state of the water channel switching device when a requested flow rate for the pump unit is less than a preset flow rate.

7. The cooling apparatus of an internal combustion engine according to claim 1,

the heat exchanger comprises a 1 st heat exchanger and a 2 nd heat exchanger;

the heat-exchange water path comprises a 1 st heat-exchange water path and a 2 nd heat-exchange water path, wherein the 1 st heat-exchange water path is configured with the 1 st heat exchanger and is arranged in parallel relative to at least one part of the circulating water path, and the 2 nd heat-exchange water path is configured with the 2 nd heat exchanger and is arranged in parallel relative to at least one part of the circulating water path;

the water path switching device comprises a 1 st water path switching device and a 2 nd water path switching device, wherein the 1 st water path switching device switches between a state in which the cooling water flows in the 1 st heat exchange water path and a state in which the cooling water does not flow in the 1 st heat exchange water path, and the 2 nd water path switching device switches between a state in which the cooling water flows in the 2 nd heat exchange water path and a state in which the cooling water does not flow in the 2 nd heat exchange water path;

the water path switching device is switched to a state in which the cooling water flows through the heat-exchange water path when the 1 st water path switching device is switched to a state in which the cooling water flows through the 1 st heat-exchange water path and the 2 nd water path switching device is switched to a state in which the cooling water flows through the 2 nd heat-exchange water path; and the number of the first and second electrodes,

the water path switching device is switched to a state in which the cooling water does not flow through the heat-exchange water path when the 1 st water path switching device is switched to a state in which the cooling water does not flow through the 1 st heat-exchange water path and the 2 nd water path switching device is switched to a state in which the cooling water does not flow through the 2 nd heat-exchange water path.

8. The cooling apparatus of an internal combustion engine according to claim 7,

the control device is configured to store, as a 1 st region, a region in which only the 1 st pump and the 2 nd pump are connected in parallel and can output a flow rate and a water pressure when the 1 st water path switching device and the 2 nd water path switching device are switched to a state in which the cooling water flows in either one of the 1 st heat-exchange water path and the 2 nd heat-exchange water path;

the control device is configured to store, as a 2 nd area, an area of a flow rate and a water pressure that can be output only by connecting the 1 st pump and the 2 nd pump in series when the 1 st water path switching device and the 2 nd water path switching device are switched to a state in which the cooling water flows in either one of the 1 st heat-exchange water path and the 2 nd heat-exchange water path;

the control device is configured to calculate a requested flow rate to the pump section and a requested water pressure to the pump section, which is determined by the requested flow rate, the state of the 1 st water channel switching device, and the state of the 2 nd water channel switching device;

the control device is configured to control the pump switching device to connect the 1 st pump and the 2 nd pump in parallel when the requested flow rate and the requested water pressure are included in the 1 st region; and the number of the first and second electrodes,

the control device is configured to control the pump switching device to connect the 1 st pump and the 2 nd pump in series when the requested flow rate and the requested water pressure are included in the 2 nd region.

9. A cooling device for an internal combustion engine, comprising:

a pump section that pressure-feeds cooling water of the internal combustion engine;

a circulation water channel including an engine water channel of the internal combustion engine, the circulation water channel being configured to connect the pump portion and the engine water channel such that the cooling water pumped from the pump portion passes through the engine water channel and returns to the pump portion again;

a heat exchanger configured to exchange heat with cooling water;

a heat-exchange water path in which the heat exchanger is disposed, the heat-exchange water path being provided in parallel with at least a part of the circulation water path;

a water passage switching device that switches between a state in which cooling water flows through the heat exchange water passage and a state in which cooling water does not flow through the heat exchange water passage; and

a control device that controls the pump section,

wherein the content of the first and second substances,

the pump section includes a 1 st pump, a 2 nd pump, and a pump switching device that switches between a state in which the 1 st pump and the 2 nd pump are connected in parallel and a state in which the 1 st pump and the 2 nd pump are connected in series,

the control device is configured to control the pump switching device to connect the 1 st pump and the 2 nd pump in parallel when the water path switching device is switched to a state in which the cooling water flows in the heat exchange water path and the cooling water flows in the circulation water path and the heat exchange water path,

the control device is configured to control the pump switching device to connect the 1 st pump and the 2 nd pump in series when the water channel switching device is switched to a state in which the cooling water does not flow in the heat exchange water channel and the cooling water flows only in the circulation water channel,

the pump section includes a 1 st pump for feeding cooling water under pressure, a 2 nd pump for feeding cooling water under pressure, an inlet water channel into which cooling water flows, an outlet water channel from which cooling water flows, a 1 st water channel in which the 1 st pump is disposed, a 2 nd water channel in which the 2 nd pump is disposed, an inter-pump water channel, a 1 st check valve, a 2 nd check valve, and a pump switching device;

the 1 st water path and the 2 nd water path are communicated with the inlet water path at branch points, are arranged in parallel with each other, and are communicated with the outlet water path at a confluence point of the 1 st water path and the 2 nd water path;

the inter-pump water passage communicates a water passage on a cooling water discharge side of the 1 st pump in the 1 st water passage with a water passage on a cooling water suction side of the 2 nd pump in the 2 nd water passage;

the 1 st check valve is disposed in the 2 nd water path between a connection portion of the 2 nd water path and the inter-pump water path and the branch point;

the 2 nd check valve is arranged in the 1 st water path between the junction of the 1 st water path and the inter-pump water path and the junction;

the pump switching device is configured in the inter-pump waterway;

the 1 st pump is disposed in the 1 st water path between a connection portion between the 1 st water path and the inter-pump water path and the branch point;

the 2 nd pump is arranged in the 2 nd water path between the connection part between the 2 nd water path and the inter-pump water path and the confluence point;

the pump switching device is an on-off valve provided in the inter-pump water passage;

the on-off valve is configured to selectively switch between a 1 st switching position for closing the inter-pump water path and a 2 nd switching position for opening the inter-pump water path; and the number of the first and second electrodes,

the control device is configured to set the on-off valve to the 1 st switching position when the 1 st pump and the 2 nd pump are connected in parallel, and set the on-off valve to the 2 nd switching position when the 1 st pump and the 2 nd pump are connected in series.

10. The cooling apparatus of an internal combustion engine according to claim 9,

the water path switching device is a thermostat which is arranged in the heat exchange water path and switches a valve opening state and a valve closing state according to the water temperature of cooling water;

the thermostat is configured such that cooling water flows through the heat exchange water passage when the thermostat is in an open state; and the number of the first and second electrodes,

the thermostat is configured to stop the flow of the cooling water to the heat exchange water passage when the thermostat is in a closed state.

11. The cooling apparatus of an internal combustion engine according to claim 9,

when the water channel switching device is switched to a state in which the cooling water flows in the heat exchange water channel, the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in parallel is larger than the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in series; and the number of the first and second electrodes,

when the water channel switching device is switched to a state in which the cooling water does not flow in the heat-exchange water channel, the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in parallel is smaller than the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in series.

12. The cooling apparatus of an internal combustion engine according to claim 10,

when the water channel switching device is switched to a state in which the cooling water flows in the heat exchange water channel, the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in parallel is larger than the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in series; and the number of the first and second electrodes,

when the water channel switching device is switched to a state in which the cooling water does not flow in the heat-exchange water channel, the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in parallel is smaller than the maximum flow rate that can be output by the pump unit by the pump switching device connecting the 1 st pump and the 2 nd pump in series.

13. The cooling apparatus of an internal combustion engine according to claim 9,

the circulation water path and the heat-exchange water path are configured such that when the water path switching device is switched to a state in which cooling water flows in the heat-exchange water path, a flow path resistance of the cooling water path is equal to or less than a reference flow path resistance, and when the water path switching device is switched to a state in which cooling water does not flow in the heat-exchange water path, the flow path resistance of the cooling water path is greater than the reference flow path resistance;

when a curve showing a relationship between a flow rate and a water pressure when a flow path resistance of the cooling water path is an arbitrary value is defined as a resistance curve, the reference flow path resistance is a flow path resistance when the resistance curve passes through an intersection of a parallel characteristic curve and a series characteristic curve;

the parallel characteristic curve is a curve showing a relationship between a maximum flow rate and a maximum water pressure that can be output by the pump section in a state where the 1 st pump and the 2 nd pump are connected in parallel; and the number of the first and second electrodes,

the series characteristic curve is a curve showing a relationship between a maximum flow rate that the pump section can output and a maximum water pressure in a state where the 1 st pump and the 2 nd pump are connected in series.

14. The cooling apparatus of an internal combustion engine according to any one of claims 9 to 13,

the control device is configured to control the pump switching device to connect the 1 st pump and the 2 nd pump in parallel and to drive only one of the 1 st pump and the 2 nd pump regardless of a state of the water channel switching device when a requested flow rate for the pump unit is less than a preset flow rate.

15. The cooling apparatus of an internal combustion engine according to claim 9,

the heat exchanger comprises a 1 st heat exchanger and a 2 nd heat exchanger;

the heat-exchange water path comprises a 1 st heat-exchange water path and a 2 nd heat-exchange water path, wherein the 1 st heat-exchange water path is configured with the 1 st heat exchanger and is arranged in parallel relative to at least one part of the circulating water path, and the 2 nd heat-exchange water path is configured with the 2 nd heat exchanger and is arranged in parallel relative to at least one part of the circulating water path;

the water path switching device comprises a 1 st water path switching device and a 2 nd water path switching device, wherein the 1 st water path switching device switches between a state in which the cooling water flows in the 1 st heat exchange water path and a state in which the cooling water does not flow in the 1 st heat exchange water path, and the 2 nd water path switching device switches between a state in which the cooling water flows in the 2 nd heat exchange water path and a state in which the cooling water does not flow in the 2 nd heat exchange water path;

the water path switching device is switched to a state in which the cooling water flows through the heat-exchange water path when the 1 st water path switching device is switched to a state in which the cooling water flows through the 1 st heat-exchange water path and the 2 nd water path switching device is switched to a state in which the cooling water flows through the 2 nd heat-exchange water path; and the number of the first and second electrodes,

the water path switching device is switched to a state in which the cooling water does not flow through the heat-exchange water path when the 1 st water path switching device is switched to a state in which the cooling water does not flow through the 1 st heat-exchange water path and the 2 nd water path switching device is switched to a state in which the cooling water does not flow through the 2 nd heat-exchange water path.

16. The cooling apparatus of an internal combustion engine according to claim 15,

the control device is configured to store, as a 1 st region, a region in which only the 1 st pump and the 2 nd pump are connected in parallel and can output a flow rate and a water pressure when the 1 st water path switching device and the 2 nd water path switching device are switched to a state in which the cooling water flows in either one of the 1 st heat-exchange water path and the 2 nd heat-exchange water path;

the control device is configured to store, as a 2 nd area, an area of a flow rate and a water pressure that can be output only by connecting the 1 st pump and the 2 nd pump in series when the 1 st water path switching device and the 2 nd water path switching device are switched to a state in which the cooling water flows in either one of the 1 st heat-exchange water path and the 2 nd heat-exchange water path;

the control device is configured to calculate a requested flow rate to the pump section and a requested water pressure to the pump section, which is determined by the requested flow rate, the state of the 1 st water channel switching device, and the state of the 2 nd water channel switching device;

the control device is configured to control the pump switching device to connect the 1 st pump and the 2 nd pump in parallel when the requested flow rate and the requested water pressure are included in the 1 st region; and the number of the first and second electrodes,

the control device is configured to control the pump switching device to connect the 1 st pump and the 2 nd pump in series when the requested flow rate and the requested water pressure are included in the 2 nd region.

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